ALBERT

Beschreibung: Uraninite solubility in 0.001–2.0 m HCl solutions was experimentally studied at 500°C, 1000 bar, and hydrogen fugacity corresponding to the Ni/NiO buffer. It was shown that the following U(IV) species dominate in the aqueous solution: U(OH)40, U(OH)2Cl20, and UOH Cl30 Using the results of uraninite solubility measurement, the Gibbs free energies of U(IV) species at 500°C and 1000 bar were calculated (kJ/mol): −9865.55 for UO2(aq), −1374.57 for U(OH)2 Cl20, and −1265.49 for UOH Cl30, and the equilibrium constants of uraninite dissolution in water and aqueous HCl solutions were estimated: UO2(cr) = UO2(aq), pK0 = 6.64; UO2(cr) + 2HCl0 = U(OH)2 Cl20, pK2 = 3.56; and UO2(cr) + 3HCl0 = UOHcl30 + H2O, pK3 = 3.05. The value pK1 ≈ 5.0 was obtained as a first approximation for the equilibrium UO2(cr) + H2O + HCl0 = U(OH)3Cl0. The constant of the reaction UO2(cr) + 4HCl0 = UCl40 + 2H2O (pK4 = 7.02) was calculated taking into account the ionization constants of U Cl40 and U(OH)40, obtained by extrapolation from 25 to 500°C at 1000 bar using the BR model. Intense dissolution and redeposition of gold (material of experimental capsules) was observed in our experiments. The analysis and modeling of this phenomenon suggested that the UO2 + x/UO2 redox pair oxidized Au(cr) to Au+(aq), which was then reduced under the influence of stronger reducers.

Beschreibung: The Norwegian Atlantic Current (NwAC) and its eddy field are examined using data from surface drifters. The data set used spans nearly 20 years, from June 1991 to December 2009. The results are largely consistent with previous estimates, which were based on data from the first decade only. With our new data set, statistical analysis of the mean fields can be calculated with larger confidence. The two branches of the NwAC, one over the continental slope and a second further offshore, are clearly captured. The Norwegian Coastal Current is also resolved. In addition, we observe a semipermanent anticylonic eddy in the Lofoten Basin, a feature seen previously in hydrography and in models. The eddy kinetic energy (EKE) is intensified along the path of the NwAC, with the largest values occurring in the Lofoten Basin. The strongest currents, exceeding 100 cm s−1, occur west of Lofoten. Lateral diffusivities were computed in five domains and ranged from 1–5 × 107 cm2 s−1. The Lagrangian integral time and space scales are 1–2 days and 7–23 km, respectively. The data set allows studies of seasonal and interannual variations as well. The strongest seasonal signal is in the NwAC itself, as the mean flow strengthens by approximately 20% in winter. The EKE and diffusivities on the other hand do not exhibit consistent seasonality in the sampled regions. There are no consistent indications of changes in either the mean or fluctuating surface velocities between the 1990s and 2000s.

Beschreibung: Regression trees represent one of the most popular tools in predictive data mining applications. However, previous studies have shown that their performances are not completely satisfactory when the dependent variable is highly skewed, and severely degrade in the presence of heavy-tailed error distributions, especially for grossly mis-measured values of the dependent variable. In this paper the lack of robustness of some classical regression trees is investigated by addressing the issue of highly-skewed and contaminated error distributions. In particular, the performances of some non robust regression trees are evaluated through a Monte Carlo experiment and compared to those of some trees, based on M-estimators, recently proposed in order to robustify this kind of methods. In conclusion, the results obtained from the analysis of a real dataset are presented.

Beschreibung: There has been a good deal of interest in the potential of marine vegetation as a sink for anthropogenic C emissions (“Blue Carbon”). Marine primary producers contribute at least 50% of the world’s carbon fixation and may account for as much as 71% of all carbon storage. In this paper, we analyse the current rate of harvesting of both commercially grown and wild-grown macroalgae, as well as their capacity for photosynthetically driven CO2 assimilation and growth. We suggest that CO2 acquisition by marine macroalgae can represent a considerable sink for anthropogenic CO2 emissions and that harvesting and appropriate use of macroalgal primary production could play a significant role in C sequestration and amelioration of greenhouse gas emissions.

Beschreibung: Inhibitors of bacterial quorum sensing have been proposed as potentially novel therapeutics for the treatment of certain bacterial diseases. We recently reported a marine Halobacillus salinus isolate that secretes secondary metabolites capable of quenching quorum sensing phenotypes in several Gram-negative reporter strains. To investigate how widespread the production of such compounds may be in the marine bacterial environment, 332 Gram-positive isolates from diverse habitats were tested for their ability to interfere with Vibrio harveyi bioluminescence, a cell signaling-regulated phenotype. Rapid assay methods were employed where environmental isolates were propagated alongside the reporter strain. “Actives” were defined as bacteria that interfered with bioluminescence without visible cell-killing effects (antibiotic activity). A total of 49 bacterial isolates interfered with bioluminescence production in the assays. Metabolite extracts were generated from cultures of the active isolates, and 28 reproduced the bioluminescence inhibition against V. harveyi. Of those 28, five extracts additionally inhibited violacein production by Chromobacterium violaceum. Chemical investigations revealed that phenethylamides and a cyclic dipeptide are two types of secondary metabolites responsible for the observed activities. The active bacterial isolates belonged primarily to either the genus Bacillus or Halobacillus. The results suggest that Gram-positive marine bacteria are worthy of further investigation for the discovery of quorum sensing antagonists.

Beschreibung: The effect of phototrophic biofilm activity on advective transport of cadmium (Cd), copper (Cu), nickel (Ni), and lead (Pb) in sandy sediments was examined using percolated columns. Cd and Ni in the effluent exhibited clear diel cycles in biofilm-containing columns, with concentrations at the end of dark periods exceeding those during illumination by up to 4.5- and 10-fold for Ni and Cd, respectively. Similar cycles were not observed for Pb or Cu. Breakthrough of the latter metals was greatly retarded and incomplete relative to Cd and Ni, and trends in biofilm treatments did not differ greatly from those in control columns. Inhibition of photosystem II by DCMU (3-(3,4-dichlorophenyl)-1,1-dimethylurea) proved that diel cycles of Cd and Ni were controlled by oxygenic photosynthesis, and microsensor measurements showed that metal cycles closely matched metabolic activity-driven pH variations. The sorption edge pH for the sand/biofilm substrate followed the order Ni 〉 Cd 〉 Cu 〉 Pb, and for Ni and Cd, was within the pH 7–10 range observed in the biofilm-containing column. Adsorption dynamics over the light periods matched pH increases, but desorption during dark periods was incomplete and slower than the rate of change of pH. Over a diel cycle, desorption was less than adsorption, resulting in net binding of dissolved metals due to the biofilm metabolic activity. Extraction with selective reagents indicated that the adsorbed metals were readily exchangeable, and potentially bioavailable. Thus, phototrophic benthic biofilms can control the transport of some metals across the sand–water interface, and processes in this very thin surficial layer should be considered when evaluating chemical fluxes in permeable sediments.

Beschreibung: On Syros, high‐pressure metamorphism affects a lithological pile that is composed of, from base to top: (1) the Komito‐Vari granitic basement, (2) a margin sedimentary sequence that is predominantly made of marbles and schists (the Pyrgos and Kastri units), and (3) the Kambos metaophiolitic mélange. The tectonic history occurred in three main stages. During the first stage, in the mid‐Eocene, the Kambos oceanic unit was thrust southward on top of the sedimentary pile. Top‐to‐the‐south‐southwest ductile senses of shear are synchronous with prograde high‐pressure metamorphism and associated with this thrusting event. The second stage corresponds to a top‐to‐the‐northeast ductile shear that affects the whole metamorphic pile and is synchronous with the metamorphic retrogression from eclogite to greenschist facies. However, the Kambos oceanic unit remained partly undeformed, as shown by significant volumes containing undeformed lawsonite pseudomorphs. No major extensional detachment related to this exhumation event outcrops on the island. The localized semibrittle to brittle deformation of the third stage is associated with the postmetamorphic development of (1) a ramp‐flat extensional system at the island scale, whose southward minimum displacement is estimated at approximately 7 km, and (2) two sets of steeply dipping strike‐slip faults with a normal component, trending either east–west or around north–south, indicating that the mean stretching and shortening directions are trending NNE–SSW and ESE–WNW, respectively. This sequence of major tectonic events and their relationship to metamorphism are interpreted within the framework of the subduction of the Pindos Ocean and then of the Adria continental passive margin.

Beschreibung: Meltponds on Arctic sea ice have previously been reported to be devoid of marine metazoans due to fresh-water conditions. The predominantly dark frequently also green and brownish meltponds observed in the Central Arctic in summer 2007 hinted to brackish conditions and considerable amounts of algae, possibly making the habitat suitable for marine metazoans. Environmental conditions in meltponds as well as sympagic meiofauna in new ice covering pond surfaces and in rotten ice on the bottom of ponds were studied, applying modified techniques from sea-ice and under-ice research. Due to the very porous structure of the rotten ice, the meltponds were usually brackish to saline, providing living conditions very similar to sub-ice water. The new ice cover on the surface had similar characteristics as the bottom layer of level ice. The ponds were thus accessible to and inhabitable by metazoans. The new ice cover and the rotten ice were inhabited by various sympagic meiofauna taxa, predominantly ciliates, rotifers, acoels, nematodes and foraminiferans. Also, sympagic amphipods were found on the bottom of meltponds. We suggest that, in consequence of global warming, brackish and saline meltponds are becoming more frequent in the Arctic, providing a new habitat to marine metazoans.

Beschreibung: Prey regurgitation during capture is a potential important confounding effect in fish dietary ecology studies as it may lead to overestimation of stomach vacuity and underestimation of prey consumption. This study investigates patterns of prey regurgitation and stomach vacuity among five grouper and three snapper species in shallow water off French Polynesia and tests the effectiveness of piercing swim-bladders after capture as a method to prevent regurgitation. Groupers exhibited a moderate overall regurgitation rate of 15.6% of full stomachs and a high true (i.e., after accounting for regurgitation) stomach vacuity rate of 40.5%. In contrast, snappers showed high regurgitation (mean 31.7%) and low true stomach vacuity (14.6%). Not accounting for regurgitation would have resulted in a moderate overestimation of stomach vacuity in groupers, but an almost 3-fold overestimation in snappers. Swim-bladder decompression by piercing after capture prove a highly effective method to reduce regurgitation (more than 2-fold for groupers and near 8-fold for snappers). This study enables a more general understanding of prey regurgitation in two commercially valuable fish families, thus improving understanding of the dietary ecology of these fishes. This information is particularly important in the context of prey consumption estimates and subsequent estimations of the impact of fish predators on ecosystems.

Beschreibung: A one-dimensional model is used to analyze, at the local scale, the response of the equatorial Atlantic Ocean under different meteorological conditions. The study was performed at the location of three moored buoys of the Pilot Research Moored Array in the Tropical Atlantic located at 10° W, 0° N; 10° W, 6° S; and 10° W, 10° S. During the EGEE-3 (Etude de la circulation océanique et de sa variabilité dans le Golfe de Guinee) campaign of May-June 2006, each buoy was visited for maintenance during 2 days. On board the ship, high-resolution atmospheric parameters were collected, as were profiles of temperature, salinity, and current. These data are used here to initialize, force, and validate a one-dimensional model in order to study the diurnal oceanic mixed-layer variability. It is shown that the diurnal variability of the sea surface temperatures is mainly driven by the solar heat flux. The diurnal response of the near-surface temperatures to daytime heating and nighttime cooling has an amplitude of a few tenths of degree. The computed diurnal heat budget experiences a net warming tendency of 31 and 27 W m‑2 at 0° N and 10° S, respectively, and a cooling tendency of 122 W m‑2 at 6° S. Both observed and simulated mixed-layer depths experience a jump between the nighttime convection phase and the well-stabilized diurnal water column. Its amplitude changes dramatically depending on the meteorological conditions occurring at the stations and reaches its maximum amplitude (~50 m) at 10° S. At 6° and 10° S, the presence of barrier layers is observed, a feature that is clearer at 10° S. Simulated turbulent kinetic energy (TKE) dissipation rates, compared to independent microstructure measurements, show that the model tracks their diurnal evolution reasonably well. It is also shown that the shear and buoyancy productions and the vertical diffusion of TKE all contribute to the supply of TKE, but the buoyancy production is the main source of TKE during the period of the simulation.

Beschreibung: The stratospheric climate and variability from simulations of sixteen chemistryclimate models is evaluated. On average the polar night jet is well reproduced though its variability is less well reproduced with a large spread between models. Polar temperature biases are less than 5 K except in the Southern Hemisphere (SH) lower stratosphere in spring. The accumulated area of low temperatures responsible for polar stratospheric cloud formation is accurately reproduced for the Antarctic but underestimated for the Arctic. The shape and position of the polar vortex is well simulated, as is the tropical upwelling in the lower stratosphere. There is a wide model spread in the frequency of major sudden stratospheric warnings (SSWs), late biases in the breakup of the SH vortex, and a weak annual cycle in the zonal wind in the tropical upper stratosphere. Quantitatively, “metrics” indicate a wide spread in model performance for most diagnostics with systematic biases in many, and poorer performance in the SH than in the Northern Hemisphere (NH). Correlations were found in the SH between errors in the final warming, polar temperatures, the leading mode of variability, and jet strength, and in the NH between errors in polar temperatures, frequency of major SSWs, and jet strength. Models with a stronger QBO have stronger tropical upwelling and a colder NH vortex. Both the qualitative and quantitative analysis indicate a number of common and long‐standing model problems, particularly related to the simulation of the SH and stratospheric variability.

Beschreibung: Somatic mutations are an underappreciated source of genetic variation within multi-cellular organisms. The resulting genetic mosaicism should be particularly abundant in large clones of vegetatively propagating angiosperms. Little is known on the abundance and ecological correlates of genetic mosaicism in field populations, despite its potential evolutionary significance. Because sexual reproduction restores genetic homogeneity, we predicted that in facultatively clonally reproducing organisms, the prevalence of genetic mosaicism increases with increasing clonality. This was tested among 33 coastal locations colonized by the ecologically important marine angiosperm Zostera marina, ranging from Portugal to Finland. Genetic mosaics were detectable as complex microsatellite genotypes at two hypervariable loci that revealed additional mosaic alleles, suggesting the presence of one or more divergent cell lineages within the same ramet. The proportions of non-mosaic genotypes in a population sharply decreased below a clonal richness of 0.2. Accordingly, more genetic mosaics were found at the southern and northern limit of the distribution of Z. marina in Europe where sexual reproduction is rare or absent. The genetic mosaics observed at neutral microsatellite markers suggest the possibility of within-clone variation at selectively relevant loci and supports the notion that members of clones are seldom genetically identical.

Beschreibung: A new species of the pelagic marine copepod family Oncaeidae, Oncaea serrulata, is described from the Mediterranean Sea. The species belongs to the notopus-group of Oncaeidae, which are characterized by a long, free exopod on leg 5. It differs from Oncaea notopus Giesbrecht 1891 and any other described species of this group by a combination of morphological characters, including: (1) the relative lengths of distal endopod spines on swimming legs 2 and 3, (2) the denticulate ornamentation of the exopod segment and the two exopodal setae on leg 5, (3) the proportional lengths of the caudal setae, and (4) the comparatively small body length. The species occurs widespread in the Mediterranean Sea in mesopelagic and deep-sea layers down to 3,000 m depth and was also found in near-bottom sediment traps moored at a bottom depth of 2,347 m in the Ligurian Sea. O. serrulata appears to be the only representative of the notopus-group in the Mediterranean Sea and seems to have consistently been confounded with the allegedly cosmopolitan O. notopus Giesbrecht in most earlier studies in this area. The taxonomic history of Giesbrecht’s O. notopus, which was originally described from the Pacific, is summarized and morphological identification parameters applicable for the species identification of notopus-type oncaeids are discussed. In the future, identification may be facilitated by using genetic barcodes in comparison with those recently analysed for the Mediterranean O. serrulata (as Oncaea sp. 7 sensu Böttger-Schnack 1997). Published data on the zoogeographical and vertical distribution as well as the abundance of notopus-type oncaeids in the Mediterranean Sea are reviewed. Possible causes for the lack of positive records of this taxon in Mediterranean studies earlier than 1980 are discussed.

Beschreibung: Geophysical datasets sensitive to different physical parameters can be used to improve resolution of Earth's internal structure. Herein, we jointly invert long-period magnetotelluric (MT) data and surface-wave dispersion curves. Our approach is based on a joint inversion using a genetic algorithm for a one-dimensional (1-D) isotropic structure, which we extend to 1-D anisotropic media. We apply our new anisotropic joint inversion to datasets from Central Germany demonstrating the capacity of our joint inversion algorithm to establish a 1-D anisotropic model that fits MT and seismic datasets simultaneously and providing new information regarding the deep structure in Central Germany. The lithosphere/asthenosphere boundary is found at approx. 84 km depth and two main anisotropic layers with coincident most conductive/seismic fast-axis direction are resolved at lower crustal and asthenospheric depths. We also quantify the amount of seismic and electrical anisotropy in the asthenosphere showing an emerging agreement between the two anisotropic coefficients.

Beschreibung: A natural carbon dioxide (CO2) seep was discovered during an expedition to the southern German North Sea (October 2008). Elevated CO2 levels of ∼10–20 times above background were detected in seawater above a natural salt dome ∼30 km north of the East-Frisian Island Juist. A single elevated value 53 times higher than background was measured, indicating a possible CO2 point source from the seafloor. Measured pH values of around 6.8 support modeled pH values for the observed high CO2 concentration. These results are presented in the context of CO2 seepage detection, in light of proposed subsurface CO2 sequestering and growing concern of ocean acidification. We explore the boundary conditions of CO2 bubble and plume seepage and potential flux paths to the atmosphere. Shallow bubble release experiments conducted in a lake combined with discrete-bubble modeling suggest that shallow CO2 outgassing will be difficult to detect as bubbles dissolve very rapidly (within meters). Bubble-plume modeling further shows that a CO2 plume will lose buoyancy quickly because of rapid bubble dissolution while the newly CO2-enriched water tends to sink toward the seabed. Results suggest that released CO2 will tend to stay near the bottom in shallow systems (〈200 m) and will vent to the atmosphere only during deep water convection (water column turnover). While isotope signatures point to a biogenic source, the exact origin is inconclusive because of dilution. This site could serve as a natural laboratory to further study the effects of carbon sequestration below the seafloor.

Beschreibung: Detailed geological and petrological-geochemical study of rocks of the lava complex of Young Shiveluch volcano made it possible to evaluate the lava volumes, the relative sequence in which the volcanic edifice was formed, and the minimum age of the onset of eruptive activity. The lavas of Young Shiveluch are predominantly magnesian andesites and basaltic andesites of a mildly potassic calc-alkaline series (SiO2 = 55.0–63.5 wt %, Mg# = 55.5–68.9). Geologic relations and data on the mineralogy and geochemistry of rocks composing the lava complex led us to conclude that the magnesian andesites of Young Shiveluch volcano are of hybrid genesis and are a mixture of silicic derivatives and a highly magnesian magma that was periodically replenished in the shallow-depth magmatic chamber. The fractional crystallization of plagioclase and hornblende at the incomplete segregation of plagioclase crystals from the fractionating magmas resulted in adakitic geochemical parameters (Sr/Y = 50–71, Y 〈 18 ppm) of the most evolved rock varieties. Our results explain the genesis of the rock series of Young Shiveluch volcano without invoking a model of the melting of the subducting Pacific slab at its edge.

Beschreibung: Reconstructions of the spatial pattern of recent multi-decadal sea level trends in the Indian Ocean (IO) indicate a zonally-extended band in the southern tropics where sea level has substantially fallen between the 1960s and 1990s; the decline is consistent with the observed subsurface cooling associated with a shoaling thermocline in this region. Here the origin and spatio-temporal characteristics of these trends are elucidated by a sequence of ocean model simulations. Whereas interannual variability in the southwestern tropical IO appears mainly governed by IO atmospheric forcing, longer term changes in the south tropical IO involve a strong contribution from the western Pacific via wave transmission of thermocline anomalies through the Indonesian Archipelago, and their subsequent westward propagation by baroclinic Rossby waves. The late 20th-century IO subsurface cooling trend reversed in the 1990s, reflecting the major regime shift in the tropical Pacific easterlies associated with the Pacific Decadal Oscillation.

Beschreibung: The pelagic marine copepod family Oncaeidae is highly diversified (over 100 species worldwide) and includes a great number of sibling species, which are difficult to identify morphologically, because of their very small size (0.18–1.2 mm total length as adults). Global investigations of oncaeid biodiversity are severely hampered by insufficient taxonomic knowledge, in particular for species which have first been described from the European Mediterranean Sea (type locality). Many of these species have been reported as key taxa of small-sized copepod communities in very distant oceanic regions. However, due to the taxonomic uncertainties it cannot be excluded that at least some of these allegedly cosmopolitan species in reality represent a complex of distinct, yet closely related, species. To improve the basis for the identification of Oncaeidae of Mediterranean origin, new diagnostic characters in combination with traditional methods were applied in the present study. Copepods were sampled with fine nets of 0.1 mm mesh size down to a maximum depth of 1,000 m on a west-east-transect in the Mediterranean Sea. Oncaeid species and form variants were predefined morphologically and the genetic identity of the morphospecies was analysed by about 650 and 500 bp region of the mitochondrial COI and 12S srRNA gene sequence, respectively (barcoding). A total of 67 individuals from 24 oncaeid species and forms were successfully analysed, including 12 species and one form of Mediterranean origin. For Oncaeidae, the 12S amplification turned out to be more successful (23 species) than the COI amplification (13 species and 1 form). Together, the morphological and molecular results are discussed with respect to three topics: (1) confirmation of a genetic distinction of three Triconia species, which have been interpreted as sibling species by morphological characters, (2) genetic distance of species within the ovalis-complex of oncaeids and (3) the taxonomic status of two form variants of Oncaea mediterranea (Claus).

Beschreibung: 18.10. - 25.10.2011

Beschreibung: A regional forest carbon budget accounting technique based on carbon pools balance with incomes from growing woodstocks and losses from harvesting, fires and other disturbances have been developed. Forest carbon budgets of the Russian administrative units during 1988–2009 have been accounted. The carbon sink to Russian forests have increased from 80 Mt C × yr−1 in 1988 to 230–240 Mt C × yr−1 in late 2000s. This tendency is explained with the decline in harvesting, which have started in 1990s. European part of Russia was found to have higher areally averaged carbon sink compared with the Asian part. It have been associated with peculiar ways of wildfires governance in these two parts.

Beschreibung: The Mw = 9.0 earthquake of 11 March 2011 at the Japan Trench and its devastating tsunami underscore the importance of understanding seismogenic behavior of subduction faults and realistically estimating the potential size of future earthquakes and tsunamis. For the Cascadia subduction zone (Figure 1a), a critical knowledge gap is the level of microseismicity offshore, especially near the megathrust, needed to better understand the state of the locked zone. In 2010 the first detailed seafloor earthquake monitoring campaign along the northern Cascadia subduction zone recorded nearby earthquakes in the local magnitude (ML) range from possibly around zero to 3.8 (Figures 1b and 1c) and larger earthquakes from outside this region. Preliminary analyses indicate that the network appears to have yielded a fairly complete catalog for events with ML 〉 1.2. Only a few tens of these events occurred beneath the continental shelf and slope (Figure 1a). The majority of the earthquakes were located along the margin-perpendicular Nootka fault zone. The relatively low seismicity away from the Nootka fault is consistent with a fully locked megathrust. Land-based GPS measurements cannot resolve the question of whether the offshore part of the megathrust seismogenic zone is narrow and fully locked or wider and only partially locked (slowly creeping). If it were only partially locked, the seafloor seismometer data should show many more small earthquakes along the interface than were actually detected.

Beschreibung: The accurate dating of meteorite impact structures on Earth has proven to be challenging. Melt sheets are amenable to high-precision dating by the U-Pb and 40Ar/39Ar methods, but many impact events do not produce them, or they are not preserved. In cases where high-temperature shock metamorphism of the target materials has occurred without widespread melting, these isotopic chronometers may be partially reset and yield dates that are difficult to interpret unambiguously as the age of impact. However, the (U-Th)/He chronometer is sensitive to thermal resetting and can provide a powerful new tool for dating impactites. We report (U-Th)/He dates for accessory minerals from the Manicouagan impact structure in Quebec, Canada. Nine zircons from a melt sheet sample yield a weighted mean age of 213.2 ± 5.4 Ma (2SE), indistinguishable from the published 214 ± 1 Ma (2σ) U-Pb zircon age for the impact. In contrast, five apatites from this sample yield dates between 205.9 ± 6.5 and 162.0 ± 5.3 Ma (2σ), indicating variable postimpact helium loss due to low-temperature thermal disturbance. Preimpact titanite crystals from a shocked meta-anorthosite sample yield two dates consistent with the impact age, at 212 ± 27 and 214 ± 13 Ma (2σ), and two younger dates of 189.6 ± 6.9 and 192.2 ± 9.8 Ma (2σ), suggestive of postimpact helium loss. These results indicate that (U-Th)/He chronometry is a suitable method for dating impact events, although interpretation of the results requires recognition of possible 4He loss related to reheating subsequent to impact.

Beschreibung: The success of the 1st International Symposium on Sponge Microbiology reflects the growing interest of the scientific community in this new and emerging field. Research themes of the symposium included symbiont diversity, physiology and function, secondary metabolites, metagenomics, single-cell genomics and other -omics approaches, sponge–symbiont interactions, sponge diseases, environmental stress, and many more. This article summarizes the major developments in the field and identifies future foci for research.

Beschreibung: Previous studies have revealed silica formation in the teeth of mandibular gnathobases of copepods while significant amounts of zinc and copper are present, which might improve mechanical stability of the teeth and represent an adaptation to compact food particles. The present study aimed at analysing the distribution and concentration of trace elements in the mandibular gnathobases of females of the Antarctic copepod species Calanoides acutus. Because of the low overall masses of few micrograms per specimen the application of a combination of position-resolved micro-beam techniques was necessary and micro-particle-induced X-ray emission spectrometry and laser ablation inductively coupled plasma mass spectrometry were used to determine Ba, Br, Ca, Cl, Cu, Fe, K, Mg, Na, Ni, P, S, Si and Zn in the samples with μm to sub-μm resolution. Calibration strategies were optimised to fit for the carbonate matrix. The analyses revealed a distinct enrichment of Br, Ca, Fe, K, S, Si and Zn in the teeth of the gnathobases.

Beschreibung: Dates of Cruise: 13. September to 19. September 2011 Projects: Student course in physical oceanography. Areas of Research: Physical oceanography Port call: Kiel – Warnemünde – Kiel

Beschreibung: Marine sponges and their associated bacteria have been proven to be a rich source of novel secondary metabolites with therapeutic usefulness in cancer, infection, and autoimmunity. In this study, 79 strains belonging to 20 genera of the order Actinomycetales and seven strains belonging to two genera of the order Sphingomonadales were cultivated from 18 different Caribbean sponges and identified by 16S rRNA gene sequencing. Seven of these strains are likely to represent novel species. Crude extracts from selected strains were found to exhibit protease inhibition against cathepsins B and L, rhodesain, and falcipain-2 as well as immunomodulatory activities such as induction of cytokine release by human peripheral blood mononuclear cells. These results highlight the significance of marine sponge-associated bacteria to produce bioactive secondary metabolites with therapeutic potential in the treatment of infectious diseases and disorders of the immune system.

Beschreibung: The aim of this study was to evaluate the potential of plant suspension cultures for the production of antimicrobial activities. The extracellular, intracellular and cell wall bound fractions of 16 heterotrophic, photoautotrophic and photomixotrophic plant cell suspension cultures each treated with nine different elicitors were tested for the elicitor dependent production of antimicrobial activities. Distinctly different patterns of bioactivities directed against a panel of human isolates including Gram-positive (Bacillus subtilis, Staphylococcus aureus) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa) bacteria as well as fungi (Candida maltosa) were identified for all except the two autotrophic cell cultures. The intracellular fractions of elicited cell cultures were more active than extracellular fractions while cell wall bound fractions showed almost no activities. The intracellular fraction of heterotrophic Lavendula angustifolia cells elicited with a preparation of Pseudomonas syringae was the most active fraction against Candida maltosa. The intracellular fraction of photomixotrophic Arabidopsis thaliana cells elicited with salicylic acid was active against all test isolates. An antimicrobial protein could be identified and partially purified from this culture. Our findings suggest that elicited plant cell cultures may present a new promising alternative source of antimicrobial proteins.

Beschreibung: Independent methods of geological and molecular-biological chronologies have made it possible to define generally corresponding stages in the geological and biological evolution of the environments and communities of Lake Baikal since the Late Cretaceous, i.e., during the last 70 myr. All the abiotic elements drastically changed during geological evolution, with destruction of existing and formation of new natural complexes. Nevertheless, some specific zones retained relicts of former settings. The resulting present-day natural complex includes elements of different ages and geneses. Similar to different natural zones of the present-day Earth, which are populated by different biocoenoses, stages in the development of abiotic elements are also characterized by different faunal and floral assemblages. Some taxa were replaced by others, and the resulting aqueous biota of Lake Baikal includes different-age and ecologically different elements. The oldest groups of Baikal organisms appeared approximately 70 Ma ago, although the largest proportion of the lake biota started forming 4–3 Ma ago in response to the most drastic changes in the abiotic elements of the environment. The youngest taxa appeared 1.8 to 0.15 Ma ago, i.e., during the period when superdeep lake environments and mountainous glaciations were developing. The chronological coincidence of main stages in development of abiotic and biotic elements of the nature indicates their relationships. Particular transformations of abiotic elements and the probable mechanism of their influence on the evolution of living communities are also considered.

Beschreibung: There is an incomplete description of the mid-depth circulation and its link to the oxygen minimum zone (OMZ) in the eastern tropical South Pacific. Subsurface currents of the OMZ in the eastern tropical South Pacific are investigated with a focus at 400 m depth, close to the core of the OMZ, using several Acoustic Doppler Current Profiler sections recorded in January and February 2009. Five profiling floats with oxygen sensors were deployed along 85°50’W in February 2009 with a drift depth at 400 m. Their spreading paths are compared with the model flow field from a 1/10° Tropical Pacific model (TROPAC01) and the Simple Ocean Data Assimilation (SODA) model. Overall the mean currents in the eastern tropical South Pacific are weak so that eddy variability influences the flow and ultimately feed oxygen-poor water to the OMZ. The center of the OMZ is a stagnant area so that floats stay much longer in this region and can even reverse direction. In one case of one float deployed at 8°S returned to the same location after 15 month. On the northern side of the OMZ in the equatorial current system, floats move rapidly to the west. Most current bands reported for the near surface layer exist also in the depth range of the OMZ. A schematic circulation flow field for the OMZ core depth is derived which shows the northern part of the South Pacific subtropical gyre south of the OMZ and the complicated zonal equatorial flow field north of the OMZ.

Beschreibung: Background: Seagrasses are a polyphyletic group of monocotyledonous angiosperms that have adapted to a completely submerged lifestyle in marine waters. Here, we exploit two collections of expressed sequence tags (ESTs) of two wide-spread and ecologically important seagrass species, the Mediterranean seagrass Posidonia oceanica (L.) Delile and the eelgrass Zostera marina L., which have independently evolved from aquatic ancestors. This replicated, yet independent evolutionary history facilitates the identification of traits that may have evolved in parallel and are possible instrumental candidates for adaptation to a marine habitat. Results: In our study, we provide the first quantitative perspective on molecular adaptations in two seagrass species. By constructing orthologous gene clusters shared between two seagrasses (Z. marina and P. oceanica) and eight distantly related terrestrial angiosperm species, 51 genes could be identified with detection of positive selection along the seagrass branches of the phylogenetic tree. Characterization of these positively selected genes using KEGG pathways and the Gene Ontology uncovered that these genes are mostly involved in translation, metabolism, and photosynthesis. Conclusions: These results provide first insights into which seagrass genes have diverged from their terrestrial counterparts via an initial aquatic stage characteristic of the order and to the derived fully-marine stage characteristic of seagrasses. We discuss how adaptive changes in these processes may have contributed to the evolution towards an aquatic and marine existence.

Beschreibung: Cold-water coral ecosystems are characterised by a high diversity and population density. Living and dead foraminiferal assemblages from 20 surface sediment samples from Galway and Propeller Mounds were analysed to describe the distribution patterns of benthic foraminifera on coral mounds in relation to different sedimentary facies. Hard substrates were examined to assess the foraminiferal microhabitats and diversities in the coral framework. We recognised 131 different species, of which 27 prefer an attached lifestyle. Epibenthic species are the main constituents of the living and dead foraminiferal assemblages. The frequent species Discanomalina coronata was associated with coral rubble, Cibicides refulgens showed preference to the off-mound sand veneer, and Uvigerina mediterranea displayed abundance maxima in the main depositional area on the southern flank of Galway Mound, and in the muds around Propeller Mound. The distribution of these species is rather governed by their specific ecological demands and microhabitat availability than by the sedimentary facies. Benthic foraminiferal assemblages from coral mounds fit well into basin-wide-scale distribution patterns of species along the western European continental margin. The diversity of the foraminiferal faunas is not higher on the carbonate mounds as in their vicinity. The living assemblages show a broad mid-slope diversity maximum between 500 and 1,300 m water depth, which is the depth interval of coral mound formation at the Celtic and Amorican Margin. The foraminiferal diversity maximum is about 700 m shallower than comparable maxima of nematodes and bivalves. This suggests that different processes are driving the foraminiferal and metazoan diversity patterns.

Beschreibung: The ongoing warming of bottom water in the Arctic region is anticipated to destabilize some of the gas hydrate present in shallow seafloor sediment, potentially causing the release of methane from dissociating hydrate into the ocean and the atmosphere. Ocean-bottom seismometer (OBS) experiments were conducted along the continental margin of western Svalbard to quantify the amount of methane present as hydrate or gas beneath the seabed. P- and S-wave velocities were modeled for five sites along the continental margin, using ray-trace forward modeling. Two southern sites were located in the vicinity of a 30 km long zone where methane gas bubbles escaping from the seafloor were observed during the cruise. The three remaining sites were located along an E-W orientated line in the north of the margin. At the deepest northern site, Vp anomalies indicate the presence of hydrate in the sediment immediately overlying a zone containing free gas up to 100-m thick. The acoustic impedance contrast between the two zones forms a bottom-simulating reflector (BSR) at approximately 195 m below the seabed. The two other sites within the gas hydrate stability zone (GHSZ) do not show the clear presence of a BSR or of gas hydrate. However, anomalously low Vp, indicating the presence of free gas, was modeled for both sites. The hydrate content was estimated from Vp and Vs, using effective-medium theory. At the deepest northern site, modeling suggests a pore-space hydrate concentration of 7–12%, if hydrate forms as part of a connected framework, and about 22% if it is pore-filling. At the two other northern sites, located between the deepest site and the landward limit of the GHSZ, we suggest that hydrate is present in the sediment as inclusions. Hydrate may be present in small quantities at these two sites (4–5%) of the pore space. The variation in lithology for the three sites indicated by high-resolution seismic profiles may control the distribution, concentration and formation of hydrate and free gas.

Beschreibung: The continental margin off Uruguay and northern Argentina is characterized by high fluvial input by the de la Plata River and a complex oceanographic regime. Here we present first results from RV Meteor Cruise M78/3 of May–July 2009, which overall aimed at investigating sediment transport processes from the coast to the deep sea by means of hydroacoustic and seismic mapping, as well as coring using conventional tools and the new MARUM seafloor drill rig (MeBo). Various mechanisms of sediment instabilities were identified based on geophysical and core data, documenting particularly the continental slope offshore Uruguay to be locus of submarine landsliding. Individual landslides are relatively small with volumes 〈2km3. Gravitational downslope sediment transport also occurs through the prominent Mar del Plata Canyon and several smaller canyons. The canyons originate at a midslope position, and the absence of buried upslope continuations strongly suggests upslope erosion as main process for canyon evolution. Many other morphological features (e.g., slope-parallel scarps with scour geometries) and abundant contourites in a 35-m-long MeBo core reveal that sediment transport and erosion are controlled predominantly by strong contour currents. Despite numerous landslide events, their geohazard potential is considered to be relatively small, because of their small volumes and their occurrence at relatively deep water depths of more than 1,500 m.

Beschreibung: We have studied the distribution and community composition of denitrifying bacteria in the stratified water column and at the sediment–water interface in lakes Plußsee and Schöhsee, and a near-shore site in the Baltic Sea in Germany. Although environmental changes induced by the stratification of the water column in marine environments are known to affect specific populations of denitrifying bacteria, little information is available for stratified freshwater lakes and brackish water. The aim of the present study was to fill this gap and to demonstrate specific distribution patterns of denitrifying bacteria in specific aquatic habitats using two functional markers for the nitrite reductase (nirK and nirS genes) as a proxy for the communities. The leading question to be answered was whether communities containing the genes nirK and nirS have similar, identical, or different distribution patterns, and occupy the same or different ecological niches. The genes nirK and nirS were analyzed by PCR amplification with specific primers followed by terminal restriction fragment length polymorphism (T-RFLP) and by cloning and sequence analysis. Overall, nirS-denitrifiers were more diverse than nirK-denitrifiers. Denitrifying communities in sediments were clearly different from those in the water column in all aquatic systems, regardless of the gene analyzed. A differential distribution of denitrifying assemblages was observed for each particular site. In the Baltic Sea and Lake Plußsee, nirK-denitrifiers were more diverse throughout the water column, while nirS-denitrifiers were more diverse in the sediment. In Lake Schöhsee, nirS-denitrifiers showed high diversity across the whole water body. Habitat-specific clusters of nirS sequences were observed for the freshwater lakes, while nirK sequences from both freshwater lakes and the Baltic Sea were found in common phylogenetic clusters. These results demonstrated differences in the distribution of bacteria containing nirS and those containing nirK indicating that both types of denitrifiers apparently occupy different ecological niches.

Beschreibung: [1] The Integrated Ocean Drilling Program (IODP) Expedition 310 recovered drill cores from the drowned reefs around the island of Tahiti (17°40′S, 149°30′W), many of which contained samples of massive corals from the genus Porites. Herein we report on one well-preserved fossil coral sample: a 13.6 cm long Porites sp. dated by uranium series techniques at 9523 ± 33 years. Monthly δ18O and Sr/Ca determinations reveal nine clear and robust annual cycles. Coral δ18O and Sr/Ca determinations estimate a mean temperature of ∼24.3°C (∼3.2°C colder than modern) for Tahiti at 9.5 ka; however, this estimate is viewed with caution since potential sources of cold bias in coral geochemistry remain to be resolved. The interannual variability in coral δ18O is similar between the 9.5 ka coral record and a modern record from nearby Moorea. The seasonal cycle in coral Sr/Ca is approximately the same or greater in the 9.5 ka coral record than in modern coral records from Tahiti. Paired analysis of coral δ18O and Sr/Ca indicates cold/wet (warm/dry) interannual anomalies, opposite from those observed in the modern instrumental record.

Beschreibung: Arctic Ocean freshening can exert a controlling influence on global climate, triggering strong feedbacks on ocean‐atmospheric processes and affecting the global cycling of the world’s oceans. Glacier‐fed ocean currents such as the Alaska Coastal Current are important sources of freshwater for the Bering Sea shelf, and may also influence the Arctic Ocean freshwater budget. Instrumental data indicate a multiyear freshening episode of the Alaska Coastal Current in the early 21st century. It is uncertain whether this freshening is part of natural multidecadal climate variability or a unique feature of anthropogenically induced warming. In order to answer this, a better understanding of past variations in the Alaska Coastal Current is needed. However, continuous long‐term high‐resolution observations of the Alaska Coastal Current have only been available for the last 2 decades. In this study, specimens of the long‐lived crustose coralline alga Clathromorphum nereostratum were collected within the pathway of the Alaska Coastal Current and utilized as archives of past temperature and salinity. Results indicate that coralline algal Mg/Ca ratios provide a 60 year record of sea surface temperatures and track changes of the Pacific Decadal Oscillation, a pattern of decadal‐to‐multidecadal ocean‐atmosphere climate variability centered over the North Pacific. Algal Ba/Ca ratios (used as indicators of coastal freshwater runoff) are inversely correlated to instrumentally measured Alaska Coastal Current salinity and record the period of freshening from 2001 to 2006. Similar multiyear freshening events are not evident in the earlier portion of the 60 year Ba/Ca record. This suggests that the 21st century freshening of the Alaska Coastal Current is a unique feature related to increasing glacial melt and precipitation on mainland Alaska.

Beschreibung: There is an evidence of the increasing intensity as well as occurrence frequency of the so-called central Pacific (CP) El Niño events since the 1990s. We examine whether such an increase in the frequency of CP El Niño may be a manifestation of natural climate variability. A control simulation of the Kiel Climate Model, run for 4200 years with the present values of greenhouse gases, exhibit large variations of the occurrence frequency of the CP El Niño versus the eastern Pacific (EP) El Niño. A model simulates to some extent changes in the occurrence ratio of CP and EP El Niño in comparison with the observations. Therefore, we can not exclude the possibility that an increasing of occurrence frequency of CP El Niño during recent decades in the observation could be a part of natural variability in the tropical climate system.

Beschreibung: Blue mussel individuals (Mytilus edulis) were cultured at four different salinities (17, 20, 29, and 34). During the course of the experiment, temperature was gradually increased from 6°C to 14°C. Mg/Ca and Sr/Ca ratios of the shell calcite portions produced during the 9 weeks of experimental treatment as well parts that were precipitated before the treatment phase were measured by laser ablation–multicollector–inductively coupled plasma–mass spectrometry. Mg/Ca ratios show a positive correlation with temperature for individuals cultured at salinity 29 and 34 (Mg/Ca (mmol/mol) ∼ (0.2–0.3)*T (°C)), while for individuals cultured at low salinities (17, 20) no trend was observed. Sr/Ca ratios were not affected by temperature but strongly by salinity. The data show very strong biological influence (“individual differences” and “physiological variability”) on elemental ratios (79% on Mg/Ca and 41% on Sr/Ca) in M. edulis calcite. The results challenge the use of blue mussel shell data as environmental proxies.

Beschreibung: New high-resolution multichannel seismic data GWADASEIS-2009 and JC45/46-2010 cruises; 72 and 60 channels, respectively) combined with previous data(AGUADOMAR-1999 and CARAVAL-2002; 6 and 24 channels, respectively) allow a detailed investigation of mass-wasting processes around the volcanic island of Montserrat in the Lesser Antilles. Seven submarine deposits have sources on the flanks of Montserrat, while three are related to the nearby Kahouanne submarine volcanoes. The most voluminous deposit (∼20 km3) within the Bouillante-Montserrat half-graben has not been described previously and is probably related to a flank instability of the Centre Hills Volcano on Montserrat, while other events are related to the younger South Soufrière Hills-Soufrière Hills volcanic complex. All deposits are located to the south or southeast of the island in an area delimited by faults of the Bouillante-Montserrat half-graben. They cover a large part of the southeast quarter of the surrounding seafloor (∼520 km2), with a total volume of ∼40 km3. Our observations suggest that the Bouillante-Montserrat half-graben exerts a control on the extent and propagation of the most voluminous deposits. We propose an interpretation for mass-wasting processes around Montserrat similar to what has happened for the southern islands of the Lesser Antilles.

Beschreibung: A global Earth System model is employed to investigate the role of direct temperature effects in the response of marine ecosystems to climate change. While model configurations with and without consideration of explicit temperature effects can reproduce observed current biogeochemical tracer distributions and estimated carbon export about equally well, carbon flow through the model ecosystem reveals strong temperature sensitivities. Depending on whether biological processes are assumed temperature sensitive or not, simulated marine net primary production (NPP) increases or decreases under projected climate change driven by a business-as-usual CO2 emission scenario for the 21st century. This suggests that indirect temperature effects such as changes in the supply of nutrients and light are not the only relevant factors to be considered when modeling the response of marine ecosystems to climate change. A better understanding of direct temperature effects on marine ecosystems is required before even the direction of change in NPP can be reliably predicted.

Beschreibung: Mud volcanoes are seafloor expressions of focused fluid flow that are common in compressional tectonic settings. New high-resolution 3-D seismic data from the Mercator mud volcano (MMV) and an adjacent buried mud volcano (BMV) image the internal structure of the top 800 m of sediment at both mud volcanoes, revealing that both are linked and have been active episodically. The total volumes of extruded mud range between 0.15 and 0.35 km3 and 0.02–0.05 km3 for the MMV and the BMV, respectively. The pore water composition of surface sediment samples suggests that halokinesis has played an important role in the evolution of the mud volcanoes. We propose that erosion of the top of the Vernadsky Ridge that underlies the mud volcanoes activated salt movement, triggering deep migration of fluids, dissolution of salt, and sediment liquefaction and mobilization since the end of the Pliocene. Since beginning of mud volcanism in this area, the mud volcanoes erupted four times while there was only one reactivation of salt tectonics. This implies that there are other mechanisms that trigger mud eruptions. The stratigraphic relationship of mudflows from the MMV and BMV indicates that the BMV was triggered by the MMV eruptions. This may either be caused by loading-induced hydrofracturing within the BMV or due to a common feeder system for both mud volcanoes. This study shows that the mud volcanoes in the El Arraiche mud volcano field are long-lived features that erupt with intervals of several tens of thousands of years.

Beschreibung: We study the influence of synoptic scale atmospheric circulation on extreme daily precipitation across the United Kingdom, using observed time series from 689 rain gauges. To this end we employ a statistical model, that uses airflow strength, direction and vorticity as predictors for the generalised extreme value distribution of monthly precipitation maxima. The inferred relationships are connected with the dominant westerly flow, the orography, and the moisture supply from surrounding seas. We aggregated the results for individual rain gauges to regional scales to investigate the temporal variability of extreme precipitation. Airflow explains a significant fraction of the variability on subannual to decadal time scales. A large fraction of the especially heavy winter precipitation during the 1980s and 1990s in north Scotland can be attributed to a prevailing positive phase of the North Atlantic Oscillation. Our statistical model can be used for statistical downscaling and to validate regional climate model output.

Beschreibung: The 1995 eruption of Fogo (Cape Verde Islands) differed from previous eruptions by the occurrence of evolved lavas, the SW-orientation of vents, and pre-eruptive seismicity between Fogo and the adjacent (~20 km) island of Brava. We have conducted a thermobarometric and chemical study of this eruption in order to reconstruct its magma plumbing system and to test for possible connections to Brava. The bimodal eruption produced basanites (5.2–6.7 wt% MgO) and phonotephrites (2.4–2.8 wt% MgO) that are related by fractional crystallization. Clinopyroxene-melt-barometry of phenocrysts yields pressure ranges of 460–680 MPa for the basanites and 460–520 MPa for the phonotephrites. Microthermometry of CO2-dominated fluid inclusions in olivine and clinopyroxene phenocrysts yields systematically lower pressure ranges of 200–310 MPa for basanites and 270–470 MPa for phonotephrites. The combined data indicate pre-eruptive storage of the 1995 magmas within the lithospheric mantle between 16 and 24 km depth. During eruption, the ascending magmas stalled temporarily at 8–11 km depth, within the lower crust, before they ascended to the surface in a few hours as indicated by zonations of olivine phenocrysts. Our data provide no evidence for magma storage at shallow levels (〈200 MPa) or lateral magma movements beneath the Fogo-Brava platform. Sr–Nd–Pb isotope ratios of samples from Brava differ significantly from those of the 1995 and older Fogo lavas, which rules out contamination of the 1995 magmas by Brava material and indicates different mantle sources and magma plumbing systems for both islands.

Beschreibung: Geological and hydrographic records contain evidence of substantial past variations in the oxygenation of the global ocean. Numerical models predicts a future decrease of marine oxygen levels under global warming. Using a global biogeochemical-climate model in which diapycnal mixing is parametrised as the sum of the regionally heterogenous tidal and homogenous background vertical mixing, we here show that simulated total oceanic oxygen content and the extent of marine suboxia are both sensitive to the strength of background vertical mixing. Eight otherwise identical configurations of the model were spun up under pre-industrial conditions for different vertical diffusivities ranging from background values of 0.01 cm 2/s to 0.5 cm 2/s. This range corresponds to various observational estimates and to values currently used in numerical ocean circulation models. Whereas the simulated total oceanic oxygen content is larger for larger mixing intensities, the simulated suboxic volume displays a maximum at intermediate diffusivities of about 0.2 cm 2/s. The intensity of vertical mixing also determines the evolution of suboxic areas under projected 21st century CO 2 emissions: while all model configurations predict a decline in total oceanic oxygen, the simulated extent of marine suboxia shows a 21st century expansion only for mixing rates higher than 0.2 cm 2/s, whereas the suboxic volume declines for lower mixing rates despite an overall loss of marine oxygen. Differences in the poorly constrained mixing parameterisation can thus lead to qualitatively different estimates about the future evolution of marine suboxia under projected climate change.

Beschreibung: By comparison of the methane mixing ratio and the carbon isotope ratio (δ13CCH4) in Arctic air with regional background, the incremental input of CH4 in an air parcel and the source δ13CCH4 signature can be determined. Using this technique the bulk Arctic CH4 source signature of air arriving at Spitsbergen in late summer 2008 and 2009 was found to be −68‰, indicative of the dominance of a biogenic CH4 source. This is close to the source signature of CH4 emissions from boreal wetlands. In spring, when wetland was frozen, the CH4 source signature was more enriched in 13C at −53 ± 6‰ with air mass back trajectories indicating a large influence from gas field emissions in the Ob River region. Emissions of CH4 to the water column from the seabed on the Spitsbergen continental slope are occurring but none has yet been detected reaching the atmosphere. The measurements illustrate the significance of wetland emissions. Potentially, these may respond quickly and powerfully to meteorological variations and to sustained climate warming.

Beschreibung: Most of the current coupled general circulation models show a strong warm bias in the eastern Tropical Atlantic. In this paper, various sensitivity experiments with the Kiel Climate Model (KCM) are described. A largely reduced warm bias and an improved seasonal cycle in the eastern Tropical Atlantic are simulated in one particular version of KCM. By comparing the stable and well-tested standard version with the sensitivity experiments and the modified version, mechanisms contributing to the reduction of the eastern Atlantic warm bias are identified and compared to what has been proposed in literature. The error in the spring and early summer zonal winds associated with erroneous zonal precipitation seems to be the key mechanism, and large-scale coupled ocean-atmosphere feedbacks play an important role in reducing the warm bias. Improved winds in boreal spring cause the summer cooling in the eastern Tropical Atlantic (ETA) via shoaling of the thermocline and increased upwelling, and hence reduced sea surface temperature (SST). Reduced SSTs in the summer suppress convection and favor the development of low-level cloud cover in the ETA region. Subsurface ocean structure is shown to be improved, and potentially influences the development of the bias. The strong warm bias along the southeastern coastline is related to underestimation of low-level cloud cover and the associated overestimation of surface shortwave radiation in the same region. Therefore, in addition to the primarily wind forced response at the equator both changes in surface shortwave radiation and outgoing longwave radiation contribute significantly to reduction of the warm bias from summer to fall.

Beschreibung: Seismic oceanography is a new field in marine research combining expertise of proven geophysical methods with classical physical oceanography to get more insight into physical processes in the water column. An interdisciplinary working group at IFM-GEOMAR has sucessfully used the in-house expertise for deep ocean investigations.

Beschreibung: Tens of thousands of submarine volcanoes, so-called seamounts, with heights of more than a few hundred meters, exist in the world ocean. The Cape Verde archipelago is of volcanic origin and includes several prominent seamounts, which can give important information on the origin of submarine intraplate volcanism.

Beschreibung: Globally averaged sea level has risen by just under 10 cm during the last 50 years as a consequence of global warming. The rise, however, is not uniform, neither in time nor in space. Natural climate fluctuations and associated changes in the ocean currents have contributed to the inhomogeneity and is an important factor which will determine the pattern of future sea level rise. While research in the past years has focused on the global-mean trend and its attribution to the melting of glaciers and the thermal expansion of sea water under global warming, attention is shifting to the geographical pattern of sea level change. This is essential for coastal impact assessments, but has not been practical yet because ocean projections from current climate models widely diverge. The improvement of regional sea level prediction requires a better understanding of the underlying dynamical causes.

Beschreibung: The combined effects of ocean warming and acidification were compared in larvae from two populations of the cold-eurythermal spider crab Hyas araneus, from one of its southernmost populations (around Helgoland, southern North Sea, 54A degrees N, habitat temperature 3-18A degrees C; collection: January 2008, hatch: January-February 2008) and from one of its northernmost populations (Svalbard, North Atlantic, 79A degrees N, habitat temperature 0-6A degrees C; collection: July 2008, hatch: February-April 2009). Larvae were exposed to temperatures of 3, 9 and 15A degrees C combined with present-day normocapnic (380 ppm CO(2)) and projected future CO(2) concentrations (710 and 3,000 ppm CO(2)). Calcium content of whole larvae was measured in freshly hatched Zoea I and after 3, 7 and 14 days during the Megalopa stage. Significant differences between Helgoland and Svalbard Megalopae were observed at all investigated temperatures and CO(2) conditions. Under 380 ppm CO(2), the calcium content increased with rising temperature and age of the larvae. At 3 and 9A degrees C, Helgoland Megalopae accumulated more calcium than Svalbard Megalopae. Elevated CO(2) levels, especially 3,000 ppm, caused a reduction in larval calcium contents at 3 and 9A degrees C in both populations. This effect set in early, at 710 ppm CO(2) only in Svalbard Megalopae at 9A degrees C. Furthermore, at 3 and 9A degrees C Megalopae from Helgoland replenished their calcium content to normocapnic levels and more rapidly than Svalbard Megalopae. However, Svalbard Megalopae displayed higher calcium contents under 3,000 ppm CO(2) at 15A degrees C. The findings of a lower capacity for calcium incorporation in crab larvae living at the cold end of their distribution range suggests that they might be more sensitive to ocean acidification than those in temperate regions.

Beschreibung: Surface ocean iron (Fe) fertilization can affect the marine primary productivity (MPP), thereby impacting on CO2 exchanges at the atmosphere-ocean interface and eventually on climate. Mineral (aeolian or desert) dust is known to be a major atmospheric source for the surface ocean biogeochemical iron cycle, but the significance of volcanic ash is poorly constrained. We present the results of geochemical experiments aimed at determining the rapid release of Fe upon contact of pristine volcanic ash with seawater, mimicking their dry deposition into the surface ocean. Our data show that volcanic ash from both subduction zone and hot spot volcanoes (n = 44 samples) rapidly mobilized significant amounts of soluble Fe into seawater (35–340 nmol/g ash), with a suggested global mean of 200 ± 50 nmol Fe/g ash. These values are comparable to the range for desert dust in experiments at seawater pH (10–125 nmol Fe/g dust) presented in the literature (Guieu et al., 1996; Spokes et al., 1996). Combining our new Fe release data with the calculated ash flux from a selected major eruption into the ocean as a case study demonstrates that single volcanic eruptions have the potential to significantly increase the surface ocean Fe concentration within an ash fallout area. We also constrain the long-term (millennial-scale) airborne volcanic ash and mineral dust Fe flux into the Pacific Ocean by merging the Fe release data with geological flux estimates. These show that the input of volcanic ash into the Pacific Ocean (128–221 × 1015 g/ka) is within the same order of magnitude as the mineral dust input (39–519 × 1015 g/ka) (Mahowald et al., 2005). From the similarity in both Fe release and particle flux follows that the flux of soluble Fe related to the dry deposition of volcanic ash (3–75 × 109 mol/ka) is comparable to that of mineral dust (1–65 × 109 mol/ka). Our study therefore suggests that airborne volcanic ash is an important but hitherto underestimated atmospheric source for the Pacific surface ocean biogeochemical iron cycle.

Beschreibung: The broad belt of intraplate volcanism in the East Atlantic between 25° and 37° N is proposed to have formed by two adjacent hotspot tracks (the Madeira and Canary tracks) that possess systematically different isotopic signatures reflecting different mantle source compositions. To test this model, Hf isotope ratios from volcanic rocks from all individual islands and all major seamounts are presented in this study. In comparison with published Nd isotope variations (6 εNd units), 176Hf/177Hf ratios span a much larger range (14 εHf units). Samples from the proposed Madeira hotspot track have the most radiogenic Hf isotopic compositions (176Hf/177Hfm up to 0.283335), extending across the entire field for central Atlantic MORB. They form a relatively narrow, elongated trend on the Nd vs. Hf isotope diagram (stretching over 〉10 εHf units) between a depleted N-MORB-like endmember and a moderately enriched composition located on, or slightly below, the Nd–Hf mantle array, which overlaps the proposed "C" mantle component of Hanan and Graham (1996). In contrast, all samples from the Canary hotspot track plot below the mantle array (176Hf/177Hfm = 0.282943–0.283067) and form a much denser cluster with less compositional variation (~4 εHf units). The cluster falls between (1) a low Hf isotope HIMUlike endmember, (2) a more depleted composition, and (3) the moderately enriched end of the Madeira trend. The new Hf isotope data confirm the general geochemical distinction of the Canary and Madeira domains in the East Atlantic. Both domains, however, seem to share a common, moderately enriched endmember that has "C"-like isotope compositions and is believed to represent subducted, 〈1-Ga-old oceanic lithosphere (oceanic crust and possibly minor sediment addition). The lower 176Hf/177Hf ratio of the enriched, HIMU-like Canary domain endmember indicates the contribution of oceanic lithosphere with somewhat older recycling ages of 〉=1 Ga.

Beschreibung: Zooplankton are an important trophic link and a key food source for many larval fish species in estuarine ecosystems. The present study documents temporal and spatial zooplankton dynamics in Suisun Bay and the Sacramento–San Joaquin Delta—the landward portion of the San Francisco Estuary (California, USA)—over a 37-year period (1972–2008). The zooplankton community experienced major changes in species composition, largely associated with direct and indirect effects of introductions of non-native bivalve and zooplankton species. A major clam invasion and many subsequent changes in zooplankton abundance and composition coincided with an extended drought and accompanying low-flow/high-salinity conditions during 1987–1994. In the downstream mesohaline region, the historically abundant calanoid copepods and rotifers have declined significantly, but their biomass has been compensated to some extent by the introduced cyclopoid Limnothoina tetraspina. The more upstream estuary has also experienced long-term declining biomass trends, particularly of cladocerans and rotifers, although calanoid copepods have increased since the early 1990s due to the introduced Pseudodiaptomus spp. In addition, mysid biomass has dropped significantly throughout the estuary. Shifts in zooplankton species composition have also been accompanied by an observed decrease in mean zooplankton size and an inferred decrease in zooplankton food quality. These changes in the biomass, size, and possibly chemical composition of the zooplankton community imply major alterations in pelagic food web processes, including a drop in prey quantity and quality for foraging fish and an increase in the importance of the microbial food web for higher trophic levels.

Beschreibung: Stable isotope and fatty acid analyses were used to study carbon sources for animals in a submerged plant bed. Epiphytes growing on Potamogeton perfoliatus, sand microflora, and alder leaves were the most important carbon sources. The most abundant macrophyte, P. perfoliatus was unimportant as a food source. Modelling (IsoSource) showed that epiphytes were the most important food source for the most abundant benthic invertebrates, the isopod Asellus aquaticus (annual mean contribution 64%), the amphipod Gammarus pulex (66%), and the gastropod Potamopyrgus antipodarum (83%). The mean annual contributions of sand microflora were, respectively, 21, 19, and 9%; and of alder leaves, 15, 15, and 8% for these three species. The relative importance of carbon sources varied seasonally. The relative contribution of epiphytes was lowest for all three grazer species in July: A. aquaticus 38%, G. pulex 43%, and P. antipodarum 42%. A decline in epiphyte biomass in summer may have caused this switch to less attractive food sources. P. perfoliatus provided habitat and shelter for consumers, but food was mainly supplied indirectly by providing space for attached epiphytes, which are fast-growing and provide a highly nutritious food source.

Beschreibung: The volatile contents of olivine‐hosted (Fo89–71) melt inclusion glasses in rapidly quenched mafic tephras from volcanic front volcanoes of the Central American Volcanic Arc (CAVA) in Guatemala, Nicaragua, and Costa Rica, were analyzed by secondary ion mass spectrometry (SIMS) in order to derive the minimum eruptive output of CO2, along with H2O, Cl, and S. Details of the analytical method are provided that establish melt inclusion CO2 analyses with the Cameca ims6f at the Helmholtz Centre Potsdam. The highest CO2 concentrations (up to 1800 mg/g) are observed in Nicaraguan samples, while melt inclusions from Guatemala and Costa Rica have CO2 contents between 50 and 500 mg/g. CO2 does not positively covary with sediment/slab fluid tracers such as Ba/La, Ba/Th, or U/La. Instead, the highest CO2 concentrations occur in the inclusions with the most depleted incompatible element compositions and low H2O, approaching the composition of mid‐ocean ridge basalts (MORBs), whereas the most H2O‐rich inclusions are relatively CO2‐poor (〈800 mg/g). This suggests that CO2 degassing was more extensive in the melts with the highest slab contribution. CO2/Nb ratios in the least degassed CAVA melt inclusions are similar to those of primitive MORBs. These are interpreted here as recording a minimum CO2 output rate from the mantle wedge, which amounts to 2.8 × 104 g/s for the ∼1100 km long CAVA. Previously published estimates from quiescent degassing and numerical modeling, which also encompassed the slab contribution, are 3 times higher. This comparison allows us to estimate the proportion of the total CO2 output derived from the mantle wedge.

Beschreibung: The present study experimentally tested the influence of water temperature on the inclusion of 15 elements into juvenile European eel (Anguilla anguilla) otoliths in freshwater. It should be investigated (1) if temperature effects on otolith Sr/Ca might impair the interpretation of migration studies and (2) if the elemental composition of otoliths can be used to reconstruct experienced temperature histories of eels. Therefore, eels were kept under full experimental conditions at three different water temperatures (14 °C, 19 °C and 24 °C) for 105 days. Thereafter, laser ablation inductively coupled mass spectrometry (LA-ICPMS) was conducted on the outer edge of their otoliths. Our analyses revealed significant temperature effects on otolith Na/Ca, Sr/Ca, Mg/Ca, Mn/Ca, Ba/Ca, Zr/Ca and Y/Ca ratios. Variations of Sr/Ca caused by temperature were far below those used to detect eel movements between waters of different salinities and will therefore not affect the interpretation of migration studies. Elemental fingerprints of Sr/Ca, Mg/Ca, Mn/Ca and Ba/Ca ratios resulted in clearly separated groups according to temperature treatments, indicating that changes in water temperature might lead to characteristic changes in otolith element composition. However, the successful application of elemental fingerprints to reconstruct moderate changes of water temperature seems doubtful because the influence of somatic growth on otolith microchemistry still remains unclear, and temperature-induced variations could be overlaid by changes of water element concentrations during growth periods. Nevertheless, our results contribute to the completion of knowledge about factors influencing element incorporation and help to explain variations in element composition of fish otoliths.

Beschreibung: Ecological speciation has been the subject of intense research in evolutionary biology but the genetic basis of the actual mechanism driving reproductive isolation has rarely been identified. The extreme polymorphism of the major histocompatibility complex (MHC), probably maintained by parasite-mediated selection, has been proposed as a potential driver of population divergence. We performed an integrative field and experimental study using three-spined stickleback river and lake ecotypes. We characterized their parasite load and variation at MHC class II loci. Fish from lakes and rivers harbor contrasting parasite communities and populations possess different MHC allele pools that could be the result of a combined action of genetic drift and parasite-mediated selection. We show that individual MHC class II diversity varies among populations and is lower in river ecotypes. Our results suggest the action of homogenizing selection within habitat type and diverging selection between habitat types. Finally, reproductive isolation was suggested by experimental evidence: in a flow channel design females preferred assortatively the odor of their sympatric male. This demonstrates the role of olfactory cues in maintaining reproductive isolation between diverging fish ecotypes.

Beschreibung: Coastal eutrophication is thought to cause excessive growth of epiphytes in eelgrass beds, threatening the health and survival of these ecologically and economically valuable ecosystems worldwide. Mesograzers, small crustacean and gastropod grazers, have the potential to prevent seagrass loss by grazing preferentially and efficiently on epiphytes. We tested the impact of three mesograzers on epiphyte biomass and eelgrass productivity under threefold enriched nutrient concentrations in experimental indoor mesocosm systems under summer conditions. We compared the results with earlier identical experiments that were performed under ambient nutrient supply. The isopod Idotea baltica, the periwinkle Littorina littorea, and the small gastropod Rissoa membranacea significantly reduced epiphyte load under high nutrient supply with Rissoa being the most efficient grazer, but only high densities of Littorina and Rissoa had a significant positive effect on eelgrass productivity. Although all mesograzers increased epiphyte ingestion with higher nutrient load, most likely as a functional response to the quantitatively and qualitatively better food supply, the promotion of eelgrass growth by Idotea and Rissoa was diminished compared to the study performed under ambient nutrient supply. Littorina maintained the level of its positive impact on eelgrass productivity regardless of nutrient concentrations.

Beschreibung: The northern East China Sea Shelf Basin consists of three depressions (the Domi, Jeju, and Socotra Depressions), separated by basement highs or rises. Reconstruction of depth-converted seismic reflection profiles from these depressions reveals that the northern East China Sea Shelf Basin experienced two phases of rifting, followed by regional subsidence. Initial rifting in the Late Cretaceous was driven by the NW-SE crustal stretching of the Eurasian plate, caused by the subduction of the Pacific plate beneath the plate margin. Major extension (~15 km) took place during the early phase of basin formation. The initial rifting was terminated by regional uplift in the Late Eocene-Early Oligocene, which was probably due to reorganization of plate boundaries. Rifting resumed in the Early Oligocene; the magnitude of extension was mild (〈1 km) during this period. A second phase of uplift in the Early Miocene terminated the rifting, marking the transition to the postrift phase of regional subsidence. Up to 2,600 m of sediments and basement rock were removed by erosion during and after the second phase of uplift. An inversion in the Late Miocene interrupted the postrift subsidence, resulting in an extensive thrust-fold belt in the eastern part of the area. Subsequent erosion removed about 900 m of sediments. The regional subsidence has dominated the area since the Late Miocene.

Beschreibung: Arctic in Rapid Transition Implementation Workshop; Winnipeg, Manitoba, Canada, 18–20 October 2010; Rapid transitions in Arctic sea ice and the associated global integrated Earth system impacts and socioeconomic consequences have brought the Arctic Ocean to the top of national and international geophysical and political agendas. Alarmingly, there is a persistent mismatch between observed and predicted patterns, which speaks to the complexity of planning adaptation and mitigation activities in the Arctic. Predicting future conditions of Arctic marine ecosystems for climate change requires interdisciplinary and pan-Arctic characterization and understanding of past and present trends. The Arctic in Rapid Transition (ART) initiative is an integrative, international, interdisciplinary, pan-Arctic network to study spatial and temporal changes in sea ice cover and ocean circulation over broad time scales to better understand and forecast the impact of these changes on Arctic marine ecosystems and biogeochemistry. The ART initiative began in October 2008 and is still led by early-career scientists. The ART science plan, developed after the ART initiation workshop in November 2009, was endorsed by the Arctic Ocean Sciences Board, which is now the Marine Working Group of the International Arctic Science Committee.

Beschreibung: The deep structure of the south-central Costa Rican subduction zone has not been studied in great detail so far because large parts of the area are virtually inaccessible. We present a receiver function study along a transect of broadband seismometers through the northern flank of the Cordillera de Talamanca (south Costa Rica). Below Moho depths, the receiver functions image a dipping positive conversion signal. This is interpreted as the subducting Cocos Plate slab, compatible with the conversions in the individual receiver functions. In finite difference modeling, a dipping signal such as the one imaged can only be reproduced by a steeply (80°) dipping structure present at least until a depth of about 70–100 km; below this depth, the length of the slab cannot be determined because of possible scattering effects. The proposed position of the slab agrees with previous results from local seismicity, local earthquake tomography, and active seismic studies, while extending the slab location to greater depths and steeper dip angle. Along the trench, no marked change is observed in the receiver functions, suggesting that the steeply dipping slab continues until the northern flank of the Cordillera de Talamanca, in the transition region between the incoming seamount segment and Cocos Ridge. Considering the time predicted for the establishment of shallow angle underthrusting after the onset of ridge collision, the southern Costa Rican subduction zone may at present be undergoing a reconfiguration of subduction style, where the transition to shallow underthrusting may be underway but still incomplete.

Beschreibung: Differences in stress tolerance and reproductive traits may drive the competitive hierarchy between nonindigenous and indigenous species and turn the former ones into successful invaders. In the northern Baltic Sea, the non-indigenous Gammarus tigrinus is a recent invader of littoral ecosystems and now occupies comparable ecological niches as the indigenous G. zaddachi. In laboratory experiments on specimens collected between June and August 2009 around Tva¨rminne in southern Finland (59°500N/23°150E), the tolerances towards heat stress and hypoxia were determined for the two species using lethal time, LT50, as response variable. The brood size of the two species was also studied and some observations were made on maturation of juveniles. Gammarus tigrinus was more resistant to hypoxia and survived at higher temperatures than G. zaddachi. Brood size was also greater in G. tigrinus than in G. zaddachi and G. tigrinus matured at a smaller size and earlier than G. zaddachi. Hence, there are clear competitive advantages for the non-indigenous G. tigrinus compared to the indigenous G. zaddachi, and these may be further strengthened through ongoing environmental changes related to increased eutrophication and a warming climate in the Baltic Sea region.

Beschreibung: New major and trace element and Sr, Nd, and Pb isotope data, together with 39Ar-40Ar ages for lavas from the extinct Galapagos Rise spreading center in the eastern Pacific reveal the evolution in magma compositions erupted during slowdown and after the end of active spreading at a mid-ocean ridge. Lavas erupted at 9.2 Ma, immediately prior to the end of spreading are incompatible element depleted mid-ocean ridge tholeiitic basalts, whereas progressively younger (7.5 to 5.7 Ma) postspreading lavas are increasingly alkalic, have higher concentrations of incompatible elements, higher La/Yb, K/Ti, 87Sr/86Sr, and lower 143Nd/144Nd ratios and were produced by smaller degrees of mantle melting. The large, correlated variations in trace element and isotope compositions can only be explained by melting of heterogenous mantle, in which incompatible trace element enriched lithologies preferentially contribute to smaller degree mantle melts. The effects of variable degrees of melting of heterogeneous mantle on lava compositions must be taken into account when using mid-ocean ridge basalt (MORB) to infer the conditions of melting beneath active spreading ridges. For example, the stronger “garnet signature” inferred from Sm/Nd and 143Nd/144Nd ratios for postspreading lavas from the Galapagos Rise results from a larger contribution from enriched lithologies with high La/Yb and Sm/Yb, rather than from a greater proportion of melting in the stability field of garnet peridotite. Correlations between ridge depth and Sm/Yb and fractionation-corrected Na concentrations in MORB worldwide could result from variations in mantle fertility and/or variations in the average degree of melting, rather than from large variations in mantle temperature. If more fertile mantle lithologies are preferentially melted beneath active spreading ridges, then the upper mantle may be significantly more “depleted” than is generally inferred from the compositions of MORB.

Beschreibung: To understand the gradual global cooling during the mid-Pliocene (3.5–2.5 Myr ago) one needs to consider the tectonical constriction of tropical seaways, which affected ocean circulation and the evolution of climate. Here we use paired measurements of δ18O and Mg/Ca ratios of planktonic foraminifera to reconstruct the Pliocene hydrography of the western tropical Indian Ocean (Site 709C) and changes in the Leeuwin Current in the eastern subtropical Indian Ocean (Site 763A) in response to Indonesian Gateway dynamics. Today, the Indonesian Throughflow (ITF) and, subsequently, the warm southward flowing Leeuwin Current off Western Australia are essential for the polar heat transport in the Indian Ocean. During 3.5–3 Ma, sea surface temperatures significantly dropped in the Leeuwin Current area, becoming since ~3.3 Ma 2°C–3°C cooler than the rather unchanged sea surface temperatures from the eastern and western tropical Indian Ocean. We refer this drop in sea surface temperatures to a weakened Leeuwin Current with severe climatic effects on Western Australia induced by a tectonically reduced surface ITF. We suggest that this reduced surface ITF led to a diminished poleward heat transport in the Indian Ocean resulting in a weakened Leeuwin Current and possibly to cooling of the Benguela upwelling system.

Beschreibung: Modeling and proxy studies indicate that a reduction of Atlantic Meridional Overturning Circulation (AMOC) strength profoundly impacts temperatures and salinities in the (sub)tropical Atlantic, especially on subsurface levels. While previous studies focused on prominent periods of AMOC reduction during the last deglaciation, we aim to test whether similar reconfigurations of the subtropical hydrography occurred during the moderate climatic alterations punctuating the last interglacial Marine Isotope Stage (MIS) 5. Here, we present temperature and salinity records from a Florida Straits core by combining d18O and Mg/Ca analyses on surface (Globigerinoides ruber, white) and deep‐dwelling (Globorotalia crassaformis) foraminifera covering MIS 5 in high resolution. The data reveal increasing salinities at intermediate depths during interglacial cooling episodes, decoupled from relatively stable surface conditions. This probably indicates the spatial expansion of saline subtropical gyre waters due to enhanced Ekman downwelling and might also point to a changed density structure and altered geostrophic balance in Florida Straits. Notably, these oceanographic alterations are not consistently occurring during periods of AMOC reduction. The data suggest that the expansion of gyre waters into Florida Straits was impeded by the increasing influence of Antarctic Intermediate Water (AAIW) from MIS 5.5 to ∼107 kyr BP. Afterward, increasingly positive benthic d13C values imply a recession of AAIW, allowing the temporary expansion of gyre waters into Florida Straits. We argue that the inferred transient subtropical salt accumulation and warm pool expansion might have played a pivotal role in reinvigorating meridional overturning and dampen the severity of interglacial cold phases.

Beschreibung: Multi-decadal weakening trend of the equatorial Pacific easterly winds since 1960 has reversed after 1993. The trend reversal has induced cooling (shallow thermocline) trend in the equatorial western Pacific before 1993, followed by a warming (deep thermocline) trend from 1993 to the present. All available atmospheric reanalysis products corroborate the trend reversal during the two multi-decadal periods. The magnitudes of the multi-decadal trends of the easterly winds, however, differ among the reanalysis products. The trend reversals of regional ocean circulations are assessed using linear regressions between wind and transport anomalies in an eddy-permitting numerical model, suggesting that since 1993 the Indonesian Throughflow and the Leeuwin Current transports have also reversed their multi-decadal weakening trends. Key Points: - There have been reversals of the multi-decadal weakening trends of trade winds - Different reanalysis products capture different trends in trade winds

Beschreibung: In recent years, thicklip grey mullet Chelon labrosus has shown increasing expansion of its native habitats in the north-eastern Atlantic into northerly adjacent areas including the North Sea and the brackish Baltic Sea. Despite the regular annual and seasonal occurrence of C. labrosus in the western Baltic during the warm months, nothing is known of the origin or whereabouts of the mullet during the cold season. As different possible migration scenarios can be considered, we performed otolith microchemistry analyses on specimens from the western Baltic Sea to identify the origin of this nonindigenous species. Comparison with North Sea samples revealed common habitat preferences and underlined the highly euryhaline nature of C. labrosus in different recently occupied habitats. Occasional fluctuations of Sr/Ca ratio along the growth axis suggest periodical migration between waters of different salinities but did not reveal distinct migration pathways.

Beschreibung: The paper presents data on naturally quenched melt inclusions in olivine (Fo 69–84) from Late Pleistocene pyroclastic rocks of Zhupanovsky volcano in the frontal zone of the Eastern Volcanic Belt of Kamchatka. The composition of the melt inclusions provides insight into the latest crystallization stages (~70% crystallization) of the parental melt (~46.4wt%SiO2, ~2.5wt%H2O, ~0.3wt%S), which proceeded at decompression and started at a depth of approximately 10 km from the surface. The crystallization temperature was estimated at 1100 ± 20°C at an oxygen fugacity of ΔFMQ = 0.9–1.7. The melts evolved due to the simultaneous crystallization of olivine, plagioclase, pyroxene, chromite, and magnetite (Ol : Pl : Cpx : (Crt–Mt) ~ 13 : 54 : 24 : 4) along the tholeiite evolutionary trend and became progressively enriched in FeO, SiO2, Na2O, and K2O and depleted in MgO, CaO, and Al2O3. Melt crystallization was associated with the segregation of fluid rich in S-bearing compounds and, to a lesser extent, in H2O and Cl. The primary melt of Zhupanovsky volcano (whose composition was estimated from data on the most primitive melt inclusions) had a composition of low-Si (~45wt%SiO2) picrobasalt (~14wt%MgO), as is typical of parental melts in Kamchatka and other island arcs, and was different from MORB. This primary melt could be derived by ~8% melting of mantle peridotite of composition close to the MORB source, under pressures of 1.5 ± 0.2 GPa and temperatures 20–30°C lower than the solidus temperature of “dry” peridotite (1230–1240°C). Melting was induced by the interaction of the hot peridotite with a hydrous component that was brought to the mantle from the subducted slab and was also responsible for the enrichment of the Zhupanovsky magmas in LREE, LILE, B, Cl, Th, U, and Pb. The hydrous component in the magma source of Zhupanovsky volcano was produced by the partial slab melting under water-saturated conditions at temperatures of 760–810°C and pressures of ~3.5 GPa. As the depth of the subducted slab beneath Kamchatkan volcanoes varies from 100 to 125 km, the composition of the hydrous component drastically changes from relatively low-temperature H2O-rich fluid to higher temperature H2O-bearing melt. The geothermal gradient at the surface of the slab within the depth range of 100–125 km beneath Kamchatka was estimated at 4°C/km.

Beschreibung: Ammonia and Elphidium collected in the Kiel Fjord for the present study were first identified on morphological bases as Ammonia beccarii (Linne´, 1758) and Elphidium excavatum (Terquem, 1876). Phylogenetic analyses based on partial SSU rDNA and LSU rDNA sequences show that Ammonia specimens sampled in the Kiel Fjord belong to the phylotype T6, which has a disjunct distribution (Wadden and Baltic Seas/China and Japan) and has been identified as Ammonia aomoriensis (Asano, 1951). Partial SSU rDNA sequence analyses indicate that Elphidium specimens from the Kiel Fjord belong to the clade E. excavatum, confirming the morphological identification. This clade can be further divided in three subclades. Kiel Fjord Elphidium belong to two of these subclades and were identified morphologically as the subspecies E. excavatum excavatum (Terquem, 1876) and E. e. clavatum Cushman, 1930.

Beschreibung: Satellite images document a decrease in Arctic ice cover in summer by 40% during the past 30 years. However, responsible processes and possible consequences of this decrease are little understood. The joint Russian-German project „Laptev Sea Polynya“ is coordinated by IFM-GEOMAR and aims to ascertain the causes and consequences of climate change and its essential mechanisms in the Arctic. Now the project scientists revealed a changed water mass distribution in the Siberian Laptev Sea which might be of consequence for ice formation in the whole Arctic.

Beschreibung: Stratospheric sudden warmings (SSWs) are a major source of variability during Northern Hemisphere winter. The frequency of occurrence of SSWs is influenced by El Niño–Southern Oscillation (ENSO), the quasi-biennial oscillation (QBO), the 11 year solar cycle, and volcanic eruptions. This study investigates the role of ENSO and the QBO on the frequency of SSWs using the National Center for Atmospheric Research's Whole Atmosphere Community Climate Model, version 3.5 (WACCM3.5). In addition to a control simulation, WACCM3.5 simulations with different combinations of natural variability factors such as the QBO and variable sea surface temperatures (SSTs) are performed to investigate the role of QBO and ENSO. Removing only one forcing, variable SSTs or QBO, yields a SSW frequency similar to that in the control experiment; however, removing both forcings results in a significantly decreased SSW frequency. These results imply nonlinear interactions between ENSO and QBO signals in the polar stratosphere during Northern Hemisphere winter. This study also suggests that ENSO and QBO force SSWs differently. The QBO forces SSW events that are very intense and whose impact on the stratospheric temperature can be seen between December and June, whereas ENSO forces less intense SSWs whose response is primarily confined to the months of January, February, and March. The effects of SSWs on the stratospheric background climate is also addressed here. Key Points: - ENSO or QBO is needed to reproduce a realistic frequency of SSWs in a GCM - SSWs caused by ENSO and QBO have a different signature on stratospheric temperature - Mean stratospheric climate is greatly different if ENSO and QBO are removed

Beschreibung: Surface delta(15)N(PON) increased 3.92 +/- 0.48 over the course of 20 days following additions of iron (Fe) to an eddy in close proximity to the Antarctic Polar Front in the Atlantic sector of the Southern Ocean. The change in delta(15)N(PON) was associated with an increase in the 〉20 mu m size fraction, leading to a maximal difference of 6.23 between the 〉20 mu m and 〈20 mu m size fractions. Surface delta(13)C(POC) increased 1.18 +/- 0.31 over the same period. After a decrease in particulate organic matter in the surface layer, a second phytoplankton community developed that accumulated less biomass, had a slower growth rate and was characterized by an offset of 1.56 in delta(13)C(POC) relative to the first community. During growth of the second community, surface delta(13)C(POC) further increased 0.83 +/- 0.13. Here we speculate on ways that carboxylation, nitrogen assimilation, substrate pool enrichment and community composition may have contributed to the gradual increase in delta(13)C(POC) associated with phytoplankton biomass accumulation, as well as the systematic offset in delta(13)C(POC) between the two phytoplankton communities.

Beschreibung: Climate change research with the economic methodology of cost–benefit analysis is challenging because of valuation and ethical issues associated with the long delays between CO2 emissions and much of their potential damages, typically of several centuries. The large uncertainties with which climate change impacts are known today and the possibly temporary nature of some envisaged CO2 abatement options exacerbate this challenge. For example, potential leakage of CO2 from geological reservoirs, after this greenhouse gas has been stored artificially underground for climate control reasons, requires an analysis in which the uncertain climatic consequences of leakage are valued over many centuries. We here present a discussion of some of the relevant questions in this context and provide calculations with the top–down energy-environment-economy model DEMETER. Given the long-term features of the climate change conundrum as well as of technologies that can contribute to its solution, we considered it necessary extending DEMETER to cover a period from today until the year 3000, a time span so far hardly investigated with integrated assessment models of climate change.

Beschreibung: Climate warming will affect the phytoplankton spring bloom. Experiments conducted at IFM-GEOMAR indicate, that bloom biomass of phytoplankton will become less, average cell size will become smaller, the biological carbon pump will be weakened and the timing of the bloom will be advanced a bit in a warming climate.

Beschreibung: The passive NW-African continental margin is characterized by several very large but infrequent landslides. Most of these landslides occurred during periods of low or rising sea level. Hence, the probability of future large-scale slope failures during the current sea level high stand is generally considered to be low. This interpretation is challenged by new observations during a recent research cruise to the Sahara Slide.

Beschreibung: The cold waters of the polar seas are naturally low in carbonate saturation. As uptake of anthropogenic CO2 continues to acidify the oceans worldwide, the Arctic Ocean will be the first to pass the chemical threshold where surface seawater becomes undersaturated, i.e. corrosive for unprotected shells and skeletons of calcifying organisms. While the overall impacts of ocean acidification on the Arctic ecosystems are still unknown, the predicted changes in seawater chemistry are expected to make it increasingly difficult for calcareous organisms to inhabit these regions.

Beschreibung: The Collaborative Research Centre 574: Fluids and Volatiles in Subduction Zones has the overarching goal to understand the role and fate of volatiles and fluids in the entire subduction system. The SONNE cruise SO-210 was the last major expedition of the 12-year programme.

Beschreibung: Correlating metal to calcium (Me/Ca) ratios of marine biogenic carbonates, such as bivalve shells, to environmental parameters has led to contradictory results. Biogenic carbonates represent complex composites of organic and inorganic phases. Some elements are incorporated preferentially into organic phases, and others are incorporated into inorganic phases. Chemical sample pretreatment to remove the organic matrix prior to trace element analysis may increase the applicability of the investigated proxy relationship, though its efficiency and side effects remain questionable. We treated inorganic calcium carbonate and bivalve shell powder (Arctica islandica) with eight different chemical treatments including H2O2, NaOH, NaOCl, and acetone and analyzed the effects on (1) Me/Ca ratios (Sr/Ca, Mg/Ca, Ba/Ca, and Mn/Ca), (2) organic matter (≈N) content, and (3) mineralogical composition of the calcium carbonate. The different treatments (1) cause element and treatment specific changes of Me/Ca ratios, (2) vary in their efficiency to remove organic matter, and (3) can even alter the phase composition of the calcium carbonate (e.g., formation of Ca(OH)2 during NaOH treatment). Among all examined treatments there were none without any side effects. In addition, certain Me/Ca changes we observed upon chemical treatment contradict our expectations that lattice-bound elements (Sr and Ba) should not be affected, whereas non-lattice-bound elements (Mg and Mn) should decrease upon removal of the organic matrix. For instance, we observe that NaOCl treatment did not alter Sr/Ca ratios but caused unexpected changes of the Mg/Ca ratios. The latter demonstrates that the buildup of complex biogenic composites like the shell of Arctica islandica are still poorly understood.

Beschreibung: Carbon capture and storage (CCS), both on- and offshore, is expected to be an important technique to mitigate anthropogenic effects on global climate by isolating man-made carbon dioxide (CO2) in deep geological formations. In marine environments, however, the potential impacts of CO2 leakage, appropriate detection methods, and risk and pathways of atmospheric emissions are poorly defined. The natural CO2 gas seeps that occur in the relatively shallow waters off the coast of Panarea Island (Aeolian Islands, Italy) can be studied as a large-scale, real-world analogue of what might occur at a leaking offshore CCS site and what tools can be used to study it. The oceanographic survey PaCO2 was performed aboard R/V Urania from 27 July – 01 August 2011 (Naples – Naples). The project’s ship-time was funded by Eurofleets, with work being performed as a sub-project of the Seventh Framework Programme projects “ECO2” and “RISCS”, which provided subsidiary funding. Large amounts of data and samples were collected during the cruise which will be interpreted in the coming months, with preliminary results detailed here. Of particular importance was the discovery of much larger areas showing gas seepage than previously reported. Interdisciplinary measurements were performed at the Panarea seepage site. The international team of scientists onboard R/V Urania performed complementary sampling and measurements for biological, chemical, and physical parameters throughout the area. Together with the dedication of R/V Urania’s Captain and crew, and the eagerness and cooperation of the scientific crew, we were able to obtain excellent scientific results during this six-day cruise.

Beschreibung: Coral responses to degrading water quality are highly variable between species and depend on their trophic plasticity, acclimatization potential, and stress resistance. To assess the nutritional status and metabolism of the common scleractinian coral, Stylophora subseriata, in situ experiments were carried along a eutrophication gradient in Spermonde Archipelago, Indonesia. Coral fragments were incubated in light and dark chambers to measure photosynthesis, respiration, and calcification in a number of shallow reefs along the gradient. Chlorophyll a (chl a), protein content, maximum quantum yield (Fv/Fm), and effective quantum yield (U PS II) were measured on the zooxanthellae, in addition to host tissue protein content and biomass. Photosynthetic rates were 2.5-fold higher near-shore than mid-shelf due to higher areal zooxanthellae and chl a concentrations and a higher photochemical efficiency (U PS II). A 2- and 3-fold increase in areal host tissue protein and biomass was found, indicating a higher nutritional supply in coastal waters. Dark respiration, however, showed no corresponding changes. There was a weak correlation between calcification and photosynthesis (Pearson r = 0.386) and a lack of metabolic stress, as indicated by constant respiration and Fv/Fm and the ‘‘clean’’ and healthy appearance of the colonies in spite of high turbidity in near-shore waters. The latter suggests that part of the energetic gains through increased auto- and heterotrophy were spent on metabolic expenditures, e.g., mucus production. While coastal pollution is always deleterious to the reef ecosystem as a whole, our results show that the effect on corals may not always be negative. Thus, S. subseriata may be one of the few examples of corals actually profiting from land-based sources of pollution.

Beschreibung: We developed thermal models for the Chile subduction zone along two profiles at 38.2°S and 42°S within the rupture area of the 1960 M = 9.5 Valdivia earthquake and south of the 2010 M = 8.8 Maule earthquake. The age difference of the subducting Nazca Plate has a major impact on the thermal regime, being much younger and hotter in the south. Seafloor heat flow observations confirm this difference but also indicate that in the southern area, heat advection at the outer rise cools the incoming plate. Heat flow values derived from the depth of gas hydrate bottom-simulating reflectors are in general agreement with probe and borehole measurements. The positions where the plate interface reaches temperatures of 100–150°C and 350–450°C differ between the two profiles. If these temperatures control the updip and downdip limits of the interplate seismogenic zone, the seismogenic zone widens and shifts landward to greater depths from south to north. Observed microseismicity, however, seems to fade at temperatures much lower than 350–450°C. This discrepancy can be explained in three alternative ways: (1) deformation in a thick subduction channel controls the seismic/aseismic transition; (2) microseismicity recorded over a limited time period does not represent the rupture depth of large interface earthquakes; or (3) the serpentinized mantle wedge controls the downdip limit.

Beschreibung: Within the Subantarctic Mode Water (SAMW) density level, we study temporal changes in salinity, nutrients, oxygen and TTD (Transit Time Distribution) ages in the western (W) and eastern (E) subtropical gyre of the Indian Ocean (IO) from 1987 to 2002. Additionally, changes in Total Alkalinity (TA) and Dissolved Inorganic Carbon (DIC) are evaluated between 1995 and 2002. The mechanisms behind the detected changes are discussed along with the results from a hindcast model run (Community Climate System Model). The increasing salinity and decreasing oxygen trends from 1960 to 1987 reversed from 1987 to 2002 along the gyre. In the W-IO a decreasing trend in TTD ages points to a faster delivery of SAMW, thus less biogenic matter remineralization, explaining the oxygen increase and noisier nutrients decrease. In the E-IO SAMW, no change in TTD ages was detected, therefore the trends in oxygen and inorganic nutrients relate to changes in the Antarctic Surface Water transported into the E-IO SAMW formation area. In the W-IO between 1995 and 2002, the DIC increase is equal or even less than the anthropogenic input as the reduction in remineralization contributes to mask the increasing trend. In the E-IO between 1995 and 2002, DIC decreases slightly despite the increase in the anthropogenic input. Differences in the preformed E-IO SAMW conditions would explain this behavior. Trends in the W and E IO SAMW are decoupled and related to different forcing mechanisms in the two main sites of SAMW formation in the IO, at 40°S–70°E and 45°S–90°E, respectively.

Beschreibung: The powerful eruption in the Akademii Nauk caldera on January 2, 1996, marked a new activity phase of Karymsky volcano and became a noticeable event in the history of modern volcanism in Kamchatka. The paper reports data obtained by studying more than 200 glassy melt inclusions in phenocrysts of olivine (Fo82–72), plagioclase (An92–73), and clinopyroxene (Mg# 83–70) in basalts of the 1996 eruption. The data were utilized to estimate the composition of the parental melt and the physicochemical parameters of the magma evolution. According to our data, the parental melt corresponded to low magnesian, highly aluminous basalt (SiO2 = 50.2 wt %, MgO = 5.6 wt %, Al2O3 = 17 wt %) of the mildly potassic type (K2O = 0.56 wt %) and contained much dissolved volatile components (H2O = 2.8 wt %, S = 0.17 wt %, and Cl = 0.11 wt %). Melt inclusions in the minerals are similar in chemical composition, a fact testifying that the minerals crystallized simultaneously with one another. Their crystallization started at a pressure of approximately 1.5 kbar, pro ceeded within a narrow temperature range of 1040 ± 20°C, and continued until a nearsurface pressure of approximately 100 bar was reached. The degree of crystallization of the parental melt during its eruption was close to 55%. Massive crystallization was triggered by H2O degassing under a pressure of less than 1 kbar. Magma degassing in an open system resulted in the escape of 82% H2O, 93% S, and 24% Cl (of their initial contents in the parental melt) to the fluid phase. The release of volatile compounds to the atmosphere during the eruption that lasted for 18 h was estimated at 1.7 × 106 t H2O, 1.4 × 105 t S, and 1.5 × 104 t Cl. The concen trations of most incompatible trace elements in the melt inclusions are close to those in the rocks and to the expected fractional differentiation trend. Melt inclusions in the plagioclase were found to be selectively enriched in Li. The Lienriched plagioclase with melt inclusions thought to originate from cumulate layers in the feeding system beneath Karymsky volcano, in which plagioclase interacted with Lirich melts/brines and was subsequently entrapped and entrained by the magma during the 1996 eruption.

Beschreibung: On the basis of a multi-proxy data set from the Gulf of Guinea (eastern equatorial Atlantic) we reconstruct the spatio-temporal evolution of the West African monsoon (WAM) and present evidence for a decoupling between latitudinal shifts of the rain belt and WAM intensification. The onset of deglacial monsoon invigoration at ∼16,600 years before present lagged northward migration of a weak rainfall zone by ∼2800 years. Conversely, during the Younger Dryas (YD) time interval, WAM precipitation was severely reduced but we find no evidence for a large-scale retreat of the rainfall front. This observation is not in agreement with the hypothesis of a large-scale shift of the intertropical convergence zone south of the tropical WAM region during the YD. Our results can be better reconciled with the newly emerging concept of a strong influence of Tropical Easterly and African Easterly Jets on modern WAM.

Beschreibung: The Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) on board the Canadian SCISAT-1 satellite (launched in August 2003) measures over 30 different atmospheric species, including six nitrogen trace gases that are needed to quantify the stratospheric NOy budget. We combine volume mixing ratio (VMR) profiles for NO, NO2, HNO3, N2O5, ClONO2, and HNO4 to determine a zonally averaged NOy climatology on monthly and 3 month combined means (December–February, March–May, June–August, and September–November) at 5° latitude spacing and on 33 pressure surfaces. Peak NOy VMR concentrations (15–20 ppbv) are situated at about 3 hPa (∼40 km) in the tropics, while they are typically lower at about 10 hPa (∼30 km) in the midlatitudes. Mean NOy VMRs are similar in both the northern and southern polar regions, with the exception of large enhancements periodically observed in the upper stratosphere and lower mesosphere. These are primarily due to enhancements of NO due to energetic particle precipitation and downward transport. Other features in the NOy budget are related to descent in the polar vortex, heterogeneous chemistry, and denitrification processes. Comparison of the ACE-FTS NOy budget is made to both the Odin and ATMOS NOy data sets, showing in both cases a good level of agreement, such that relative differences are typically better than 20%. The NOy climatological products are available through the ACE website and are a supplement to the paper. - A middle-atmosphere NOy climatology has been produced using ACE-FTS measurements; - A robust method for quality controlling the input data has been developed - Good agreement is found between ACE-FTS NOy climatology and other climatologies

Beschreibung: It is widely accepted that the Central and Eastern Mediterranean are remnants of the Neo-Tethys. However, the orientation and timing of spreading of this domain remain controversial. Here, we present time migrated and pre-stack depth migrated NW-SE oriented Archimede (1997) lines together with the PrisMed01 (1993) profile to constrain the evolution of the Ionian basin. Our interpretation allows us to identify a large-scale set of SW-NE striking reverse faults beneath the Ionian Abyssal Plain. These primarily NW vergent faults are characterized by a spacing comprised between 10 to 20 km and a dip ranging from 60 to 65{degree sign}. Following very recent paleogeographic reconstructions, we propose that the set of N{degree sign}55 features initially formed as normal faults during the NW-SE trending seafloor spreading of the Ionian basin after its late Triassic-early Jurassic rifting. Based on geometric comparisons with the intraplate deformation observed beneath the Central Indian Ocean, we show that the inherited oceanic normal faults were reactivated under compression as reverse faults. Well-developed Tortonian syntectonic basins developed NW of the major faults and the base of the Messinian evaporites (Mobile Unit) is slightly folded by the activity of the faults. We show that 3-4 km of total shortening occurs over a 80 km wide area beneath the Ionian Abyssal Plain, resulting in a bulk shortening of 3.5-5 %. We propose a link between the Tortonian-early Messinian inversion of the fault pattern and a plate tectonic reorganization prior to the main phase of back-arc opening of the Tyrrhenian domain.

Beschreibung: We analyzed the structure and evolution of the external Calabrian Arc (CA) subduction complex through an integrated geophysical approach involving multichannel and single‐channel seismic data at different scales. Pre‐stack depth migrated crustal‐scale seismic profiles have been used to reconstruct the overall geometry of the subduction complex, i.e., depth of the basal detachment, geometry and structural style of different tectonic domains, and location and geometry of major faults. High‐resolution multichannel seismic (MCS) and sub‐bottom CHIRP profiles acquired in key areas during a recent cruise, as well as multibeam data, integrate deep data and constrain the fine structure of the accretionary wedge as well as the activity of individual fault strands. We identified four main morpho‐structural domains in the subduction complex: 1) the post‐Messinian accretionary wedge; 2) a slope terrace; 3) the pre‐Messinian accretionary wedge and 4) the inner plateau. Variation of structural style and seafloor morphology in these domains are related to different tectonic processes, such as frontal accretion, out‐of-sequence thrusting, underplating and complex faulting. The CA subduction complex is segmented longitudinally into two different lobes characterized by different structural style, deformation rates and basal detachment depths. They are delimited by a NW/SE deformation zone that accommodates differential movements of the Calabrian and the Peloritan portions of CA and represent a recent phase of plate re‐organization in the central Mediterranean. Although shallow thrust‐type seismicity along the CA is lacking, we identified active deformation of the shallowest sedimentary units at the wedge front and in the inner portions of the subduction complex. This implies that subduction could be active but aseismic or with a locked fault plane. On the other hand, if underthrusting of the African plate has stopped recently, active shortening may be accommodated through more distributed deformation. Our findings have consequences on seismic hazard, since we identified tectonic structures likely to have caused large earthquakes in the past and to be the source regions for future events.

Beschreibung: Mg/Ca ratios of surface and subsurface dwelling foraminifera provide valuable information about the past temperature of the water column. Planktonic foraminifera calcify over a period of weeks to months. Therefore, the range of Mg/Ca temperatures obtained from single specimens potentially records seasonal temperature changes. We present solution-derived Mg/Ca ratios for single specimens of the planktonic foraminifera species Globigerinoides ruber (pink), Globigerinoides ruber (white), and Globorotalia inflata from a sediment trap off northwest Africa (20°45.6′N, 18°41.9′W). Cleaning of single specimens was achieved using a flow-through system in order to prevent sample loss. Mg/Ca ratios of surface dwelling G. ruber (pink) show strong seasonality linked to sea surface temperature. Mg/Ca ratios of G. ruber (white) do not show such seasonality. Subsurface dwelling G. inflata flux is largest during the main upwelling season, but Mg/Ca ratios reflect annual temperatures at intermediate water depths. The sediment trap time series suggests that changes in the range of Mg/Ca ratios exhibited by single specimens of G. ruber (pink) and G. inflata from the sedimentary record should provide information on the past temperature range under which these species calcified. Statistical analysis suggests detectable changes in the Mg/Ca range are ≥0.80 mmol/mol (G. ruber (pink)) and ≥0.34 mmol/mol (G. inflata). For G. ruber (pink), such changes would indicate changes in the seasonal sea surface temperature range 〉4°C or a shift in the main calcification and reproductive period. For G. inflata, such changes would indicate 〉1.7°C changes in the thermocline temperature or a change in the depth habitat.

Beschreibung: The ocean plays a major role in the global carbon cycle, and attempts to reconstruct past changes in the marine carbonate system are increasing. The speciation of dissolved uranium is sensitive to variations in carbonate system parameters, and previous studies have shown that this is recorded in the uranium-to-calcium ratio (U/Ca) of the calcite shells of planktonic foraminifera. Here we test whether U/Ca ratios of deep-sea benthic foraminifera are equally suited as an indicator of the carbonate system. We compare U/Ca in two common benthic foraminifer species (Planulina wuellerstorfi and Cibicidoides mundulus) from South Atlantic core top samples with the calcite saturation state (Δ[CO32−] = [CO32−]in situ − [CO32−]sat) of the ambient seawater and find significant negative correlations for both species. Compared with planktonic foraminifera, the sensitivity of U/Ca in benthic foraminifera to changes in Δ[CO32−] is about 1 order of magnitude higher. Although Δ[CO32−] exerts the dominant control on the average foraminiferal U/Ca, the intertest and intratest variability indicates the presence of additional factors forcing U/Ca.

Beschreibung: Quartz mylonites from the Tonale Fault Zone in the Alps (northern Italy) have been investigated by the Ti-in-quartz geothermometer (TitaniQ) in order to test its applicability to measure deformation temperatures. The eastern part of the Tonale Fault Zone was contact metamorphosed by the synkinematic intrusion of the Adamello pluton, forming an ∼800 m wide mylonitic shear zone, with a synkinematic temperature gradient from ∼280°C at the frictional-viscous transition to ∼700°C at the pluton contact as derived from metamorphic mineral assemblages. Deformation microstructures from quartz mylonite samples, systematically collected across the mylonitic shear zone, display the entire range of dynamic recrystallization in quartz, which comprise bulging recrystallization (BLG), subgrain rotation recrystallization (SGR), and grain boundary migration recrystallization (GBM). TitaniQ geothermometry yields the near-peak deformation temperature for quartz mylonites deformed at metamorphic temperatures above ∼540°C in the zone of GBM. However, for mylonites formed under lower temperatures in the zones of SGR and BLG, the preexisting Ti concentrations were not reset. It is suggested that this is due to the sluggish Ti volume diffusion rates below 500°C and the short duration of contact metamorphism and deformation. Even in the higher temperature samples the reequilibration of Ti-in-quartz content was achieved by grain boundary migration rather than by volume diffusion. Hence, our results show that GBM is crucial for the reequilibration of Ti-in-quartz, while quartz mylonites deformed by either BLG or SGR, which predominate in natural shear zones at greenschist facies metamorphic conditions, most likely yield inherited temperatures.